Multicolor image forming material and multicolor image forming method using the same

ABSTRACT

The invention provides a multi-color image-forming material for recording an image by using an image-receiving sheet having an image-receiving layer and at least 4 kinds of heat transfer sheets different from each other in color and comprising a support having provided thereon at least a light-to-heat conversion layer and an image-forming layer, superposing the image-forming layer of each of the thermal transfer sheet on the image-receiving layer of the image-receiving sheet, in which the image-forming layer is opposed to the image-receiving layer, and irradiating a laser light thereto to transfer the laser-irradiated area of the image-forming layer to the image-receiving layer of the image-receiving sheet, wherein the material contains a heat transfer sheet (X) having an image-forming layer containing one selected from among Pigment Red 48:1, Pigment Red 48:3, Pigment Green 7, Pigment Blue 15:6, Pigment Blue 60, Pigment Violet 23 and Pigment Orange 43, and a method for forming a multi-color image comprises using an image-receiving sheet having an image-receiving layer and at least 5 kinds of heat transfer sheets including thermal transfer sheets for a color of yellow, magenta, cyan or black and each comprising a support having provided thereon at least a light-to-heat conversion layer and an image-forming layer, superposing the image-forming layer of each of the thermal transfer sheet on the image-receiving layer of the image-receiving sheet, and irradiating a laser light thereto to transfer the laser-irradiated area of the image-forming layer to the image-receiving layer of the image-receiving sheet and effect image recording, thus providing a multi-color image having an enlarged scope of reproducible hues.

TECHNICAL FIELD

[0001] The present invention relates to a multi-color image-formingmaterial for forming a full-color image with a high resolution using alaser light, and to a method for forming a multi-color image using thesame. In particular, the invention relates to a multi-colorimage-forming material useful for producing a color proof (DDCP: DirectDigital Color Proof) in the printing field or a mask image based ondigital image signals by laser recording and to a method for producing amulti-color image using the same.

BACKGROUND OF THE INVENTION

[0002] In the field of graphic arts, printing of a press plate has beenconducted using a set of color separation films prepared from a colororiginal by using lith type films. In general, a color proof is producedfrom color separation films, before printing (actual printing work), inorder to check for errors in the color separation step or necessity ofcolor compensation. The color proof is desired to realize an enough highresolution to permit high reproduction of a middle tone image, a highstep stability and the like. In addition, in order to obtain a colorproof similar to actual printed products, it is preferred to use, asmaterials for the color proof, those which are used for actual printedproducts—for example, regular printing papers as substrates, andpigments as coloring materials. Also, as a method for producing a colorproof, a dry method is more desired which does not use any developingsolution.

[0003] With the recent diffusion of electronic systems in thepre-printing step (pre-press field), there has been developed, as a drymethod for producing a color proof, a recording system wherein a colorproof is directly produced from digital signals. Such electronic systemintends to produce, particularly, color proofs with a high image qualityand, in general, it reproduces a half-tone dot image of 150 lines/inchor more. In order to record a high-quality proof from digital signals, alaser light which can be modulated by digital signals and permits tofinely focus the recording light is used as a recording head. Thus, ithas become necessary to develop an image-forming material which shows ahigh recording sensitivity to a laser light and an enough high resolvingpower to permit reproduction of highly fine half-tone dots.

[0004] As an image-forming material to be used for a transferimage-forming method using a laser light, there has been known aheat-melting transfer sheet comprising a support having provided thereona light-to-heat conversion layer capable of absorbing a laser light togenerate heat and an image-forming layer wherein a pigment is dispersedin a heat-meltable binder such as wax or a binder, in this order(Japanese Patent Laid-Open No. 58045/1993). In the image-forming methodusing such image-forming materials, heat generated in the laserlight-irradiated area of the light-to-heat conversion layer melts theimage-forming layer of the corresponding area, and the molten portion ofthe image-receiving layer is transferred to an image-receiving sheetdisposed, in layers, on the transfer sheet, thus a transfer image beingformed on the image-receiving sheet.

[0005] Also, Japanese Patent 219052/1994 discloses a heat transfer sheetwhich comprises a support having provided thereon a light-to-heatconversion layer containing a light-heat converting substance, anextremely thin (0.03 to 0.3 μm) heat releasable layer and animage-forming layer containing a coloring material in this order. Inthis thermal transfer sheet, the binding force between the image-forminglayer and the light-to-heat conversion layer which are bound to eachother by the heat releasable layer provided therebetween is reduced byirradiation of a laser light, and a highly fine image is formed on animage-receiving layer disposed, in layers, on the thermal transfersheet. The aforesaid image-forming method using the thermal transfersheet utilizes so-called “abrasion”. Specifically, the method utilizesthe phenomenon that the heat releasable layer is partly decomposed inthe area which has been irradiated with a laser light, and is gasified,and hence bonding force between the image-forming layer and thelight-to-heat conversion layer is so weakened in the laser-irradiatedarea that the image-forming layer in the area is transferred to theimage-receiving sheet superimposed thereon.

[0006] These image-forming methods have the advantages that regularprinting paper having provided thereon an image-receiving layer(adhesive layer) can be used as an image-receiving sheet material, andthat a multi-color image can easily be obtained by successivelytransferring images with a different color onto the image-receivingsheet. In particular, the image-forming method utilizing abrasion hasthe advantage that a highly fine image can be obtained with ease, and isuseful for producing a color proof (DDCP: Direct Digital Color Proof)ora highly fine mask image.

[0007] With the progress of DTP environment, there is an increasing needfor proof by DDCP system among users of CTP (Computer To Plate) insteadof the proof system of a conventional proof or of an analogue technique,because an intermediate film-producing step can be eliminated. In recentyears, there has been desired a large-sized DDCP having a high quality,a high stability and an excellent printing compatibility.

[0008] The laser thermal transfer method permits printing with a highresolution, and there have conventionally been such systems as (1) lasersublimation system, (2) laser abrasion system, and (3) laser meltingsystem. Howver, all of them involve the problem that form of recordedhalf-tone dots is not sharp. The laser sublimation system (1) involvesthe problem that, since it uses dyes as coloring materials, similarityto printed products is not enough and, in addition, outline of half-tonedots becomes blurred due to sublimation properties of the coloringmaterials, thus resolution not being sufficiently high. On the otherhand, the laser abrasion system shows a good similarity to printedproducts since it uses pigments as coloring materials but, since thecoloring materials are scattered in this system, outline of half-tonedots become blurred similarly with the sublimation system, thusresolution not being sufficiently high. Further, the laser meltingsystem (3) involves the problem that clear outline cannot be formed dueto flow of the molten substance.

[0009] Also, the conventionally employed thermal transfer sheets arelimited to so-called process color technique using the four colors ofyellow, magenta, cyan and black, thus the range of reproducible huesbeing limited.

[0010] The subject of the invention is to solve the aforesaid problemswith conventional art, and to attain the following objects. That is, anobject of the invention is to provide a multi-color image-formingmaterial which can reproduce an expanded range of hues, and amulti-color image-forming method using the same. Further, another objectof the invention is to provide a multi-color image-forming materialcapable of providing a large-sized DDCP having a high quality, a highstability and an excellent printing compatibility, and a multi-colorimage-forming method using the same. Also, a further object of theinvention is to provide a multi-color image-forming material which canform an image with a good image quality and a stable transfer densityeven when subjected to laser recording with a high energy by a laserlight of multi-beams, and a multi-color image-forming method using thesame.

DISCLOSURE OF THE INVENTION

[0011] That is, means to solve the aforesaid problems is as follows.

[0012] (1) A multi-color image-forming material for recording an imageby:

[0013] using an image-receiving sheet having an image-receiving layerand at least 4 kinds of heat transfer sheets, each of which is differentfrom each other in color and comprises a support having provided thereonat least a light-to-heat conversion layer and an image-forming layer;

[0014] superposing the image-forming layer in each of the thermaltransfer sheet on the image-receiving layer of the image-receivingsheet, in which the image-forming layer is opposed to theimage-receiving layer; and

[0015] irradiating a laser light thereto to transfer thelaser-irradiated area of the image-forming layer to the image-receivinglayer of the image-receiving sheet,

[0016] wherein the multi-color image-forming material includes a heattransfer sheet (X) having an image-forming layer containing one selectedfrom Pigment Red 48:1, Pigment Red 48:3, Pigment Green 7, Pigment Blue15:6, Pigment Blue 60, Pigment Violet 23 and Pigment Orange 43.

[0017] (2) The multi-color image-forming material as described in (1),wherein the thermal transfer sheet (X) is a thermal transfer sheet otherthan the thermal transfer sheet for a color of yellow, magenta, cyan orblack, and the hue of the image-forming layer is outside the scope ofhues reproducible by the single use or combined use of the thermaltransfer sheet for a color of yellow, magenta, cyan or black.

[0018] (3) The multi-color image-forming material as described in (2),wherein the image-forming layer of the thermal transfer sheet (X) has ahue of

[0019] L*=48 to 58, a*=69 to 79, b*=36 to 46;

[0020] L*=16 to 26, a*=19 to 29, b*=−63 to −73;

[0021] L*=57 to 67, a*=−73 to −83, b*=26 to 36; or

[0022] L*=65 to 75, a*=50 to 60, b*=81 to 91.

[0023] (4) The multi-color image-forming material as described in anyone of (1) to (3), wherein the transferred image has a resolution of2400 dpi or more.

[0024] (5) The multi-color image-forming material as described in (4),wherein the transferred image has a resolution of 2600 dpi or more.

[0025] (6) The multi-color image-forming material as described in anyone of (1) to (5), wherein the ratio of the optical density of thelight-to-heat conversion layer of each of the thermal transfer sheets(OD_(LH)) to the thickness of the light-to-heat conversion layer(T_(LH)): OD_(LH)/T_(LH) (unit: μm) is 4.36 or more.

[0026] (7) The multi-color image-forming material as described in anyone of (1) to (6), wherein the ratio of the optical density (OD_(I)) tothe thickness of the image-forming layer (T_(I)): OD_(I)/T_(I) (unit:μm) is 1.80 or more, in which OD_(I) represents the maximum opticaldensity among the red filter, blue filter and green filter of theimage-forming layer of each of the heat transfer sheet.

[0027] (8) The multi-color image-forming material as described in anyone of (1) to (7), wherein the recording area of the multi-color imageis of a size of 515 mm or more×728 mm or more.

[0028] (9) The multi-color image-forming material as described in (8),wherein the recording area of the multi-color image is of a size of 594mm or more×841 mm or more.

[0029] (10) The multi-color image-forming material as described in anyone of (1) to (9), wherein the contact angle of the image-forming layerof each of the thermal transfer sheet with water and the contact angleof the image-receiving layer of the image-receiving sheet with water arein the range of from 7.0 to 120.00.

[0030] (11) The multi-color image-forming material as described in anyone of (1) to (10), wherein the contact angle of the image-receivingsheet with water is 86° or less.

[0031] (12) A method for forming a multi-color image, which comprises:

[0032] using an image-receiving sheet having an image-receiving layerand at least 5 kinds of heat transfer sheets including thermal transfersheets for a color of yellow, magenta, cyan or black, each of whichcomprises a support having provided thereon at least a light-to-heatconversion layer and an image-forming layer;

[0033] superposing the image-forming layer of each of the thermaltransfer sheet on the image-receiving layer of the image-receivingsheet, in which the image-forming layer is opposed to theimage-receiving layer; and

[0034] irradiating a laser light thereto to transfer thelaser-irradiated area of the image-forming layer to the image-receivinglayer of the image-receiving sheet and record an image.

[0035] (13) The method for forming a multi-color image as described in(12), which at least uses the multi-color image-forming materialdescribed in any one of (1) to (11).

[0036] As a result of intensive investigations to provide DDCP with ahigh quality, a high stability and an excellent printing compatibilityand of a large size of B2/A2 or more, further B1/A1 or more, theinventors have developed an image-forming material of the type ofregular paper transfer, real half-tone dot output and pigment and of asize of B2 or more, and a laser thermal transfer recording system forDDP comprising an output machine and a high-quality CMS software.

[0037] The characteristic aspects of the performance of the laserthermal transfer recording system that the inventors have developed,system constitution and outline of the technical points are as follows.The characteristic aspects are: (1) Half-tone dots excellent insimilarity to printed products can be reproduced, since shape of thedots are sharp. (2) Hues are good in similarity to printed products. (3)A stable proof can be produced, since recording quality is difficultlyinfluenced by ambient temperature or humidity, and repeatedreproducibility is good. Technical points of the material which showssuch characteristic performance lie in establishment of the thin filmtransfer technique, and improvement of vacuum contact retention of thematerial, following properties to high-resolution recording and heatresistance required for the laser heat transfer system. To be specific,there may be illustrated (1) reduction of the thickness of thelight-heat converting layer by introducing an infrared ray-absorbingdye; (2) enhancement of heat resistance of the light-to-heat conversionlayer by introducing a high-Tg polymer; (3) stabilization of hue byintroducing a heat-resistant pigment; (4) control of adhesion force andcohesion force by adding wax or a low molecular component such as aninorganic pigment; and (5) imparting vacuum adhesion properties withoutdeteriorating image quality, by adding a matting agent to thelight-to-heat conversion layer. As the technical points of the system,there may be illustrated (1) air conveyance for continuously stacking anumber of sheets in a recording apparatus; (2) insertion of regularpaper on the image-receiving sheet for reducing curling after transferin a thermal transfer apparatus; and (3) connection of a general-purposeoutput driver having system connection-enlarging properties. Thus, thelaser thermal transfer recording system we have developed is constitutedby a variety of performance characteristics, system constitution andtechnical points. These are, however, only illustrative, and theinvention is not limited to these means.

[0038] We have conducted development based on the idea that individualmaterials, individual coating layers such as a light-to-heat conversionlayer, a thermal transfer layer, and an image-receiving layer, andindividual thermal transfer sheets and the image-receiving sheet shouldnot independently exist but should be constituted so as to functionorganically and comprehensively and, further, that these image-formingmaterials can exhibit their best performance when combined with arecording apparatus and a thermal transfer apparatus. We havesufficiently examined individual coating layers of the image-formingmaterial and materials constituting it, and have produced a coatinglayer which can bring out the maximum advantages of the materials tothereby produce an image-forming material, and have found appropriateranges of various physical properties where the image-forming materialcan exhibit its maximal performance. As a result, they have unexpectedlyfound a high-performance image-forming material by studying thoroughlythe relationship between individual materials, individual coating layersor individual sheets and the physical properties and organically andcomprehensively combining the image-forming material with a recordingapparatus or a thermal transfer apparatus.

[0039] The role of the invention in the system we have developed is toprovide a multi-color image-forming material exhibiting theabove-described high performance, and a method for forming a multi-colorimage using the same. The present invention is an important inventionwhich can provide a multi-color image having a hue not obtainable by theconventional process color.

[0040] That is, the multi-color image-forming material of the inventionis characterized in that it contains a thermal transfer sheet (X) havingan image-forming layer containing one selected from among Pigment Red48:1, Pigment Red 48:3, Pigment Green 7, Pigment Blue 15:6, Pigment Blue60, Pigment Violet 23 and Pigment Orange 43. One or more of the thermaltransfer sheets (X) may be used, and they are not limited as to hue.However, the hue is preferably red, blue, green or orange.

[0041] As the thermal transfer sheet (X) for a color of, for example,red, there are illustrated those which contain Pigment red 48:1 and/orPigment Red 48:3 and, as that for a color of green, there areillustrated those which contain Pigment Green 7 and, as that for a colorof blue, there are illustrated those which contain Pigment Blue 15:6and/or Pigment Blue 60 and/or Pigment Violet 23 and, as that for a colorof orange, there are illustrated those which contain Pigment Orange 43.These thermal transfer sheets (X) of individual colors may contain oneor more pigments other than the above-described ones.

[0042] Also, other thermal transfer sheets than the thermal transfersheet (X) in the multi-color image-forming material of the inventioncomprise at least three kinds of thermal transfer sheets and commonlycomprise thermal transfer sheets for a color of yellow, magenta or cyanand, further, a thermal transfer sheet for a color of black may becontained.

[0043] As the thermal transfer sheet (X), a thermal transfer sheet otherthan the thermal transfer sheet for a color of yellow, magenta, cyan orblack and which forms on the image-forming layer a hue outside the scopeof hues reproducible by the single use or combined use of the thermaltransfer sheet for a color of yellow, magenta, cyan or black ispreferred, since it more expands the scope of reproducible hues.

[0044] The hue on the image-forming layer by the thermal transfer sheet(X) (hereinafter also referred to as hue (X)) realizing the hue outsidethe scope of hues reproducible by the single use or combined use of thethermal transfer sheet for a color of yellow, magenta, cyan or black(scope of hues reproducible by so-called process color) is preferablyone of L*=48 to 58, a*=69 to 79, b*=36 to 46; L*=16 to 26, a*=19 to 29,b*=−63 to −73; L*=57 to 67, a*=−73 to −83, b*=26 to 36; or L*=65 to 75,a*=50 to 60, b*=81 to 91, wherein L*, a* and b* are elements of anL*a*b* calorimetric system.

[0045] The multi-color image-forming method of the invention ischaracterized by using at least 5 kinds of thermal transfer sheetsincluding thermal transfer sheets for a color of yellow, magenta, cyanor black, in other words, using one or more kinds of thermal transfersheets other than the thermal transfer sheets for a color of yellow,magenta, cyan or black to conduct laser thermal transfer.

[0046] The hue of the thermal transfer sheet other than the thermaltransfer sheet for a color of yellow, magenta, cyan or black is notparticularly limited as long as it is of a color different from thecolor of the image-forming layer of the thermal transfer sheet for acolor of yellow, magenta, cyan or black but, in order to enlarge thescope of reproducible hues, the hue is preferably outside the scope ofhue region reproducible by the single use or combined use of the thermaltransfer sheet for a color of yellow, magenta, cyan or black. Thethermal transfer sheet (X) capable of realizing the above-described hue(X) is illustrated as a preferred one.

[0047] In the multi-color image-forming method of the invention, it ispreferred to use at least the multi-color image-forming material of theinvention. That is, in the multi-color image-forming material of theinvention, it is preferred to use at least thermal transfer sheetsrespectively for colors of yellow, magenta, cyan and black as otherthermal transfer sheets than the thermal transfer sheet (X).

[0048] In the invention, the ratio of the optical density (OD_(LH)) ofthe light-to-heat conversion layer of the thermal transfer sheet andthickness (T_(LH)) of the light-to-heat conversion layer, OD_(LH)/T_(LH)(unit: μm) is preferably controlled to be 4.36 or more. There is nolimit as to the upper limit of OD_(LH)/T_(LH) and, the larger, the morepreferred. At present, however, the upper limit is about 10 inconsideration of balance with other characteristic properties.

[0049] In the invention, OD_(LH) of the thermal transfer sheet meansabsorbance of the light-to-heat conversion layer at a peak wavelength ofa laser light to be used upon recording of the image-forming material ofthe invention, and can be measured using a known spectrophotometer. Inthe invention, a UV-spectrophotometer, UV-240 (made by Kabushiki KaishaShimazu Seisakusho), was used. Also, the OD_(LH) is a value calculatedby subtracting the value for the support alone from the value for thethermal transfer sheet including the support.

[0050] OD_(LH)/T_(LH) relates to thermal conductivity, and can be anindication greatly influencing sensitivity and temperature humiditydependence of recording. By controlling OD_(LH)/T_(LH) within theabove-described scope, transfer sensitivity to the image-receiving sheetupon recording can be enhanced and, at the same time, temperaturehumidity dependence upon recording can be reduced.

[0051] That is, by increasing OD_(LH)/T_(LH), recording of image can beconducted with a resolution of preferably 2400 dpi, more preferably 2600dpi or more, and a size of a recording area of preferably 515 mm ormore×728 mm or more, more preferably 594 mm or more×841 mm or more.

[0052] Also, the thickness of the light-to-heat conversion layer ispreferably 0.03 to 1.0 μm, more preferably 0.05 to 0.5 μm.

[0053] Also, the ratio of the optical density (OD_(I)) of theimage-forming layer of the thermal transfer sheet to the thickness ofthe image-forming layer T_(I), OD_(I)/T_(I) (unit: μm), is preferably1.5 or more, more preferably 1.8 or more, particularly preferably 2.50or more. The upper limit of OD_(I)/T_(I) is not particularly limitedand, the greater, the more preferred. At present, however, the upperlimit is about 6 in consideration of other characteristic properties.

[0054] OD_(I)/T_(I) can be an indication of a transfer density of theimage-forming layer and a resolution of a transferred image. Bycontrolling OD_(I)/T_(I) within the above-described scope, there can beobtained an image with a high transfer density and a good resolution.Also, by reducing the thickness of the image-receiving layer, colorreproducibility can be improved.

[0055] OD_(I) means a reflection optical density obtained bytransferring an image transferred from the thermal transfer sheet to theimage receiving sheet further to regular paper of Tokuryo art paper, andmeasuring using a densitometer (X-rite 938; made by X-rite Co.) witheach color mode of yellow (Y), magenta (M), cyan (C), black (K) or thelike. That is, OD_(I) of each thermal transfer sheet for any color to beused in the invention means the maximal value measured through a redfilter (filter for cyan), a blue filter (filter for yellow) or a greenfilter (filter for magenta).

[0056] OD_(I) is preferably 0.5 to 3.0, more preferably 0.8 to 2.0.

[0057] Further, the contact angle of the image-forming layer of eachthermal transfer sheet to water and the contact angle of theimage-receiving layer of the image-receiving sheet to water arepreferably in the range of from 7.0 to 120.0 degrees, respectively. Thecontact angle is an indication of compatibility between theimage-forming layer and the image-receiving layer, i.e., transferproperties, and is more preferably 30.0 to 100.0°. Also, the contactangle of the image-receiving layer to water is still more preferably 86°or less. Controlling the contact angles within the above-described rangeserves to enhance transfer sensitivity and reduce temperature humiditydependence of recording properties, thus being preferred.

[0058] Also, the contact angle of the surface of each layer of theinvention to water is a value obtained by measuring using a contactangle meter, model CA-A (made by Kyowa Kaimen Kagaku K.K.)

[0059] As is described above, the characteristic aspect of the inventionlies in that a recorded image with a large size can be formed by using asurface tension reducing agent. The recording area of a multi-colorimage is preferably of a size of 515 mm or more×728 mm or more, morepreferably 594 mm or more×841 mm or more. The size of theimage-receiving sheet is 465 mm or more×686 mm or more.

[0060] Next, the whole system we have developed is described belowincluding the contents of the invention. In the system of the invention,a high resolution and a high image quality can be attained by inventingand employing a thin film thermal transfer system. The system of theinvention enables to obtain a transferred image of 2400 dpi or more,preferably 2600 dpi or more, in resolution. The term “thin film thermaltransfer system” means a system wherein a thin image-forming layer of0.01 to 0.9 μm in thickness is transferred to an image-receiving sheetin a partially non-molten state or in a scarcely molten state. That is,the recorded portion is transferred as a thin film, and hence the thusdeveloped thermal transfer system provides an extremely high resolution.In a preferred method for effectively conducting the thin film thermaltransfer, the interior of the light-to-heat conversion layer is deformedinto a shape of dome by recording with a light to thereby push up theimage-forming layer and increase adhesion force between theimage-forming layer and the image-receiving layer, thus transfer beingmade easy. When this deformation is large, the force of pushing theimage-forming layer to the image-receiving layer is large enough to maketransfer easy whereas, when small, the force of pushing theimage-forming layer to the image-receiving layer is so insufficient thatthere remain portions which cannot be sufficiently transferred. Hence,deformation preferred for the thin film transfer can be evaluated interms of the deformation ratio calculated by adding a cross-sectionalarea (a) of the recorded portion of the light-to-heat conversion layerincreased after recording with a light and a cross-sectional area (b) ofthe light-to-heat conversion layer before recording with a light,dividing the resulting numerical value by the cross-sectional area (b)of the light-to-heat conversion layer before recording with a light,then multiplying the resulting value by 100, the cross-sectional areabeing measured by observing under a laser microscope (VK8500; made byKihensu K. K.). That is, the deformation ratio={(a+b)/b}×100. Thedeformation ratio is 110% or more, preferably 125% or more, morepreferably 150% or more. When elongation at break is made large enough,the deformation ratio may be 250% or more but, usually, it is preferredto depress the deformation ratio at about 250%.

[0061] Technical points of the image-forming material in the thin filmtransfer are as follows.

[0062] 1. Compatibility of High Thermal Response with StorageProperties:

[0063] In order to attain a high image quality, transfer of sub-micronorder thin film is necessary but, in order to obtain a desired density,it is necessary to make a layer wherein a pigment is dispersed in a highconcentration, which conflicts with the thermal response. Also, thethermal response conflicts with storage properties (adhesion). Theproblem of these conflicting relations are solved by developing a novelpolymer and a novel additive.

[0064] 2. Ensuring High Vacuum Adhesion:

[0065] In the thin film transfer pursuing a high resolution, a smoothtransfer interface is preferred which, however, fails to provide asufficient vacuum adhesion. Not caught by the conventional knowledgewith respect to vacuum adhesion, a matting agent with a comparativelysmall particle size is incorporated in a layer under the image-forminglayer to thereby keep an appropriate gap between the thermal transfersheet and the image-receiving sheet, thus vacuum adhesion being impartedwithout transfer failure of the image due to the mating agent and withmaintaining the characteristic aspects of the thin film transfer.

[0066] 3. Use of a Heat-Resistant Organic Material:

[0067] The temperature of the light-to-heat conversion layer forconverting a laser light to heat upon laser recording reaches as high asabout 700° C., and the temperature of the image-forming layer containingthe pigment colorant reaches as high as about 500° C. As a material forthe light-to-heat conversion layer, there has been developed a modifiedpolyimide capable of being coated by using an organic solvent and, as apigment colorant, there has been developed a pigment which has a higherheat resistance than pigments for use in printing, and is stable and hasa proper hue.

[0068] 4. Ensuring Surface Cleanness:

[0069] In the thin film transfer, dusts between the thermal transfersheet and the image-receiving sheet can cause image defects, thuscausing serious problems. It is not sufficient to control materials,because dusts enter there into from outside the devices or upon cuttingof the materials. Thus it has been necessary to install a mechanism forremoving dusts in the devices. However, a material has been found whichpermits to keep an enough appropriate adhesion to clean the surface ofthe transfer material, and removal of dusts can be realized withoutreduction in productivity by changing the material of conveying rollers.

[0070] The whole system of the invention is described in detail below.

[0071] The invention preferably realizes a thermal transfer imagecomposed of sharp half-tone dots, and permits transfer onto regularpaper and recording of a size of B2 or larger (515 mm or more×728 mm ormore). The system is a system which permits recording of a size largerthan a size of 543 mm×765 mm which is the size of B2.

[0072] One of the advantages of the performance of the system developedby the invention is that sharp-shaped dots can be obtained. The thermaltransfer image obtained by this system can be a half-tone dot imagehaving a resolution of 2400 dpi or more corresponding to the printingline number. Each half-tone dot scarcely has blur and chip, and has sucha sharp shape that a greatly wide range of half-tone dots of fromhigh-light to shadow can be clearly formed. As a result, a high-qualityhalf-tone dot output having the same resolution as that of an imagesetter or a CTP setter is possible, thus half-tone dots and gradationwell similar to printed products being reproducible.

[0073] Also, a second advantage of the performance of the systemdeveloped by the invention is the good repeated reproducibility.

[0074] Since the shape of half-tone dots of the thermally transferredimage is so sharp that half-tone dots corresponding to the laser beamcan be reproduced with good fidelity. Also, since dependence ofrecording properties upon environmental temperature and humidity is sosmall that repeated reproducibility with stable hue and density can beobtained under an environment of a wide range of temperature andhumidity.

[0075] Further, a third advantage of the performance of the systemdeveloped by the invention is good color reproducibility. The thermallytransferred image obtained by this system is formed by colored pigmentswhich are used for printing inks, and has a good repeatedreproducibility, and hence it can realize a high-accuracy CMS (ColorManagement System).

[0076] Also, the hue of this thermally transferred image can be madealmost the same as the hue of Japan color, SWOP color or the like, i.e.,the hue of a printed product. In addition, as to how the color looksunder a different light source such as a fluorescent lamp or anincandescent lamp, it can show the same change as with printed products.

[0077] Also, the fourth advantage of the performance of the systemdeveloped by the invention is a good letter quality. The dot shape ofthe thermally transferred image obtained by this system is so sharp thatfine lines of fine letters can be reproduced with a distinct outline.

[0078] Next, technical characteristic aspects of materials used in thesystem of the invention are described in more detail below. As thethermal transfer systems for DDCP, there are (1) sublimation system, (2)abrasion system and (3) thermally melting system. The systems (1) and(2), wherein coloring materials are sublimed or scattered, providehalf-tone dots having a blurred outline. On the other hand, the system(3) does not give half-tone dots a clear outline due to the flow of themolten materials. In order to solve the new problems with the laserthermal transfer system and obtain a higher image quality, we haveincorporated the techniques described below on the basis of the thinfilm transfer technology. The first characteristic aspect of thetechniques with respect to the materials is to sharpen the shape ofhalf-tone dots. A laser light is converted to heat in the light-to-heatconversion layer, and the thus generated heat is conducted to theadjacent image-forming layer, and the image-forming layer is in turnadhered to the image-receiving layer to conduct image recording. Inorder to make the shape of half-tone dots sharp, it suffices that theheat generated by the laser light is conducted to the transfer interfacewithout diffusing in the plane direction, and that the image-forminglayer is sharply broken at the heated portion/non-heated portionboundary. For this purpose, the thickness of the light-to-heatconversion layer in the thermal transfer sheet is reduced, and dynamicproperties of the image-forming layer are controlled.

[0079] Technique 1 for sharpening the shape of half-tone dots is toreduce the thickness of the light-to-heat conversion layer. It issurmised by simulation that the temperature of the light-to-heatconversion layer instantaneously reaches about 700° C. and, whenthickness of the layer is thin, deformation or breakage is liable tooccur. When deformation or breakage occurs, there arises actual damagesthat the light-to-heat conversion layer is transferred to theimage-receiving sheet together with the image-forming layer and thatthere is formed an uneven transferred image. On the other hand, in orderto obtain a predetermined level of temperature, a light-to-heatconversion substance must be allowed to exist at a high concentration inthe layer, which causes the problem of precipitation of the pigment ormigration of the pigment to adjacent layers. As the light-to-heatconversion substance, carbon has often been used but, in the material ofthe invention, an infrared absorbing coloring material is used whichserves to reduce the amount thereof to be used in comparison withcarbon. As the binder, a polyimide series compound is introduced whichshows an enough dynamic strength even at a high temperature and wellretains the infrared absorbing coloring material.

[0080] Thus, it is preferred to reduce the thickness of thelight-to-heat conversion layer to about 0.5 μm or less by selecting aninfrared absorbing coloring material having excellent light-to-heatconversion properties and a heat resistant binder such as a polyimideseries binder.

[0081] Also, technique 2 for sharpening the shape of half-tone dots isto improve characteristic properties of the image-forming layer. Whendeformation of the light-to-heat conversion layer takes place or theimage-forming layer itself is deformed by the intense heat, theimage-forming layer transferred to the image-receiving layer generatesunevenness in thickness corresponding to the sub-scanning pattern of alaser light, and hence there results a non-uniform image and an apparentreduction in transfer density. This tendency becomes more serious as theimage-forming layer is thinner. On the other hand, when theimage-forming layer is thick, sharpness of resultant half-tone dots isdamaged, and the sensitivity is reduced.

[0082] In order to make the conflicting performances be compatible witheach other, it is preferred to improve transfer unevenness by adding alow-melting substance such as wax to the image-forming layer. Also, byadding inorganic fine particles in place of the binder to therebyproperly increase thickness of the layer, the image-forming layer can besharply broken at the boundary between heated portion and non-heatedportion, thus transfer unevenness being removed while maintainingsharpness of half-tone dots and sensitivity.

[0083] Also, the low-melting substances such as wax generally tend toooze onto the surface of the image-forming layer or crystallize, and insome cases cause problems with respect to image quality and stabilitywith time of the thermal transfer sheet.

[0084] In order to meet the problems, it is preferred to use alow-melting substance which has an Sp value slightly different from thatof the polymer in the image-forming layer. Such substance can enhancecompatibility with the polymer and can prevent separation of thelow-melting substance from the image-forming layer. Also, it ispreferred to mix several kinds of low-melting substances different fromeach other in structure to form an eutectic mixture which serves toprevent crystallization. As a result, there can be obtained an imagewherein the shape of half-tone dots is sharp and which forms lessunevenness.

[0085] Also, a second characteristic aspect of the techniques withrespect to the materials lies in the finding that there exists atemperature humidity dependence of the recording sensitivity. Ingeneral, dynamic physical properties and thermal physical properties arechanged when the coating layer of the thermal transfer sheet absorbsmoisture, and there arises humidity dependence of recording environment.

[0086] In order to reduce the temperature humidity dependence, it ispreferred to make the coloring material/binder system of thelight-to-heat conversion layer and the binder system of theimage-forming layer to be an organic solvent system. Also, it ispreferred to select polyvinyl butyral as a binder for theimage-receiving layer and introduce a polymer-hydrophilizing techniquefor reducing its water absorption. As the polymer-hydrophilizingtechnique, there are illustrated the technique of reacting hydroxylgroups with hydrophobic groups as described in Japanese Patent Laid-OpenNo. 238858/1996 or the technique of crosslinking two or more hydroxylgroups with a hardener.

[0087] A third characteristic aspect of the techniques with respect tothe materials lies in the improvement of similarity to printed productswith respect to hue. The following problems newly arising with the laserthermal transfer system are solved in addition to the problem on colormatching and stable dispersion of pigments with respect to thermal headsystem color proof (e.g., First Proof made by Fuji Photo Film Co.,Ltd.). That is, technique 1 for improving similarity to printed productswith respect to hue lies in the use of highly heat-resistant pigments.Usually, a heat of about 500° C. or higher is applied to theimage-forming layer upon printing by exposure with a laser light, andsome of conventionally used pigments are decomposed by the heat. Thisthermal decomposition can be prevented by employing highlyheat-resistant pigments in the image-forming layer.

[0088] And, technique 2 for improving similarity to printed productswith respect to hue is to prevent diffusion of the infrared absorbingcoloring materials. In order to prevent change of hue by migration ofthe infrared absorbing coloring material from the light-to-heatconversion layer to the image-forming layer due to the intense heat uponprinting, it is preferred to design the light-to-heat conversion layeremploying the combination of infrared absorbing coloring material/bindershowing a strong retaining force as has been described hereinbefore.

[0089] A fourth characteristic aspect of the techniques with respect tothe materials is an increased sensitivity. In general, high-speedprinting gets into energy insufficiency and, in particular, spacegenerates corresponding to the interval of sub-scanning of a laserlight. As has been described hereinbefore, the increased density ofcoloring material in the light-to-heat conversion layer and reduction inthickness of the light-to-heat conversion layer and the image-forminglayer serve to enhance efficiency of heat generation/heat conduction.Further, it is preferred to add a low-melting substance to theimage-forming layer for the purpose of obtaining the effect of theimage-forming layer slightly flowing upon heating to fill up the gapsand enhancing adhesion to the image-receiving layer. Also, it ispreferred to employ, as a binder for the image-receiving layer, forexample, the same polyvinyl butyral as that used in the image-forminglayer for the purpose of enhancing adhesion properties between theimage-receiving layer and the image-forming layer and impartingsufficient strength of a transferred image.

[0090] A fifth characteristic aspect of the techniques with respect tothe materials is improvement of vacuum adhesion properties. It ispreferred to retain the image-receiving sheet and the thermal transfersheet on a drum by vacuum adhesion. This vacuum adhesion is ofimportance since image transfer behavior is extremely sensitive to theclearance between the image-receiving layer surface of theimage-receiving sheet and the image-forming layer surface of thetransfer sheet because the image is formed by controlling adhesion forceof the two sheets. When the clearance between the materials is increaseddue to the presence of a foreign matter such as dust, there resultsimage defect or unevenness of image transfer.

[0091] In order to prevent such image defect or unevenness of imagetransfer, it is preferred to form a uniform unevenness on the thermaltransfer sheet to thereby realize good passage of the air and obtain auniform clearance.

[0092] Technique 1 for improving vacuum adhesion is to make uneven thesurface of the thermal transfer sheet. In order to obtain sufficienteffect of vacuum adhesion even in the case of printing two or morecolors in a superimposing manner, the unevenness is provided on thethermal transfer sheet. As methods for providing unevenness on thethermal transfer sheet, there are generally illustrated post-treatmentsuch as emboss treatment and addition of a matting agent to the coatinglayer. However, in order to simplify the production steps and stabilizethe materials with time, addition of a matting agent is preferred. Asthe matting agent, those which have a size larger than the thickness ofthe coating layer are required. Since addition of a matting agent to theimage-forming layer causes the problem that an image portion where thematting agent exists is missing. Thus, it is preferred to add a mattingagent having an optimal particle size to the light-to-heat conversionlayer, whereby the image-forming layer itself has an almost uniformthickness, and a defect-free image can be formed on the image-receivingsheet.

[0093] Next, the characteristic aspects of the systematizing techniquesof the system of the invention are described below. A firstcharacteristic aspect of the systematizing techniques is a constitutionof a recording apparatus. In order to surely reproduce half-tone dotshaving the above-described sharpness, the recording apparatus isrequired to be designed with a high accuracy. It has the samefundamental constitution as that of a conventional laser thermaltransfer recording apparatus. This constitution is a so-called heat-modeouter drum recording system wherein a recording head equipped with aplurality of high-powered laser beams irradiates the thermal transfersheet and the image-receiving sheet fixed on a drum with a laser lightto conduct recording. Of those, the following embodiments are preferredconstitutions.

[0094] Constitution 1 of the recording apparatus is to avoid inclusionof dust. The image-receiving sheet and the thermal transfer sheet arefed by a fully-automatic roll feeding. Since sheet feeding of a smallnumber of sheets causes inclusion of dust generated from human body,roll feeding is employed.

[0095] Since one roll of the thermal transfer sheet corresponds to onecolor, the rolls for respective colors are changed by rotating a loadingunit. Each film is cut into a predetermined length during loading, thenfixed onto a drum. Constitution 2 of the recording apparatus is tostrengthen adhesion between the image-receiving sheet and the thermaltransfer sheet on the recording drum. Fixing of the image-receivingsheet and the thermal transfer sheet onto the recording drum is effectedby vacuum suction. Fixing through mechanical means fails to strengthenthe adhesion force between the image-receiving sheet and the thermaltransfer sheet, and hence vacuum suction was employed. A number ofvacuum suction holes are formed on the recording drum, and the inside ofthe drum is vacuumized by a blower or a vacuum pump to thereby adsorbthe sheets to the drum. Since the thermal transfer sheet is adsorbed viathe adsorbed image-forming sheet, the size of the thermal transfer sheetis made larger than the size of the image-receiving sheet. The airbetween the thermal transfer sheet and the image-receiving sheet whichmost largely influences the recording performance is sucked through thearea outside the image-receiving sheet where only the thermal transfersheet exists.

[0096] Constitution 3 of the recording apparatus is to stack a pluralityof sheets on a discharge support. In the apparatus, many large-sizedsheets of B2 size or larger can be stacked one over the other on thedischarge support. When a subsequent sheet B is discharged on theimage-receiving layer of an already stacked film A, the two sometimesstick together due to the thermal adhesion thereof. When such stickingtakes place, the next sheet cannot be normally discharged, resulting injamming, thus being problematical. In order to avoid the sticking, it isbest to prevent contact between film A and film B. As countermeasuresfor preventing the contact, there have been known several methods. Thatis, there are (a) a method of providing a difference in level on thedischarge support to make the film shape non-flat and generate a gapbetween the two films, (b) a method of providing a discharge outlet at aposition higher than the discharge support, thus the films are droppedfrom above, and (c) a method of blowing an air between the two films tothereby set the next-discharged film afloat. In this system, the sheetsize is as large as B2, and hence methods (a) and (b) require anextremely large structure, thus the air-blowing method (c) beingemployed. For this reason, the method of blowing an air between the twosheets to thereby set the next-discharged sheet afloat is to beemployed.

[0097] An example of the constitution of this apparatus is shown in FIG.2.

[0098] A sequence of forming a full-color image by applying theimage-forming material to the apparatus (hereinafter referred to as“image-forming sequence of this system”) is described below.

[0099] 1) The sub-scanning axis of a recording head 2 in the recordingapparatus 1 is reset along a sub-scanning rail 3, and the main-scanningrevolving shaft of a recording drum 4 and a thermal transfersheet-loading unit 5 are reset to the starting point.

[0100] 2) An image-receiving sheet roll 6 is unwound by means ofconveying rollers 7, and the top end of the image-receiving sheet isfixed on the recording drum 4 by vacuum suction through suctioning holesprovided in the recording drum.

[0101] 3) A squeeze roller 8 migrates downward onto the recording drum 4to press down the image-receiving sheet and, when the image-receivingsheet is further conveyed over a predetermined distance by rotation ofthe drum, the sheet is cut into a predetermined length by means of acutter 9.

[0102]4) The recording drum 4 rotates one more time to complete loadingof the image-receiving sheet.

[0103] 5) Next, a thermal transfer sheet K for the first color of blackis unrolled from a thermal transfer sheet roll 10K, cut and loaded inthe same sequence as with the image-receiving sheet.

[0104] 6) Next, the recording drum 4 starts to rotate at a high speed,and the recording head 2 on the sub-scanning rail 3 starts to move and,when the head reaches the recording-starting position, a recording laseris irradiated onto the recording drum 4 by means of the recording headaccording to recording image signals. The irradiation is discontinued ata recording-completing position, and movement of the sub-scanning railand rotation of the drum are stopped. The recording head on thesub-scanning rail is reset to the starting point.

[0105] 7) The thermal transfer sheet K alone is peeled off, with leavingthe image-receiving sheet on the recording drum. For this purpose, thetip of the thermal transfer sheet is clawed by a claw and pulled in thedischarging direction, then discharged into a waste box 35 through awaste outlet 32.

[0106] 8) The procedures 5) to 7) are repeated with respect to theremaining 4 colors or more. The recording order is, for example, black,cyan, magenta, yellow, red or, further, blue, orange, etc. That is, athermal transfer sheet C for the second color of cyan is unrolled from athermal transfer sheet roll 10C, a thermal transfer sheet M for thethird color of magenta is unrolled from a thermal transfer sheet roll10M, a fourth transfer sheet Y for the fourth color of yellow isunrolled from a thermal transfer sheet roll 10Y, and the fifth transfersheet R for the fifth color of red is unrolled from a thermal transfersheet roll 10R. This order is the reverse of general printing, becausethe order of the colors on regular paper is reversed in the steptransferring onto regular paper to be conducted later. Additionally, theabove-described order is not limitative at all.

[0107] 9) When the above-described steps are completed, the recordedimage-receiving sheet is finally discharged onto a discharge support 31.The image-receiving sheet is peeled off in the same manner as with thethermal transfer sheet in 7) but, as is different from the thermaltransfer sheets, the image-receiving sheet is not discarded, and, whenadvanced to the waste outlet 32, it is returned to the dischargesupport. Upon being discharged onto the discharge support, air 34 isblown from under the discharge outlet 33 to permit stacking of aplurality of the image-receiving sheets.

[0108] It is preferred to use an adhesive roller having provided on thesurface thereof an adhesive material as a roller 7 located at a positionof either feeding or conveying the thermal transfer sheet roll and theimage-receiving sheet roll.

[0109] By providing the adhesive roller, the surface of the thermaltransfer sheet and the surface of the image-receiving sheet can becleaned.

[0110] As the adhesive materials to be provided on the surface of theadhesive roller, there are illustrated an ethylene-vinyl acetatecopolymer, an ethylene-ethyl acrylate copolymer, a polyolefin resin, apolybutadiene resin, a styrene-butadiene copolymer (SBR), astyrene-ethylene-butene-styrene copolymer, an acrylonitrile-butadienecopolymer (NBR), a polyisoprene resin (IR), a styrene-isoprene copolymer(SIS), an acrylicester copolymer, a polyester resin, a polyurethaneresin, an acryl resin, butyl rubber, polynorbornene, etc.

[0111] The adhesive roller can clean the surface of the thermal transfersheet and the surface of the image-receiving sheet by coming intocontact therewith. The contact pressure is not particularly limited solong as they are in contact with each other.

[0112] Vickers hardness of the adhesive material to be used for theadhesive roller, Hv, is preferably 50 kg/mm² (≈490 MPa) or less thanthat, because such material permits to sufficiently remove the foreignmatter of dust and depressing image defects.

[0113] Vickers hardness is a hardness obtained by measuring hardnessusing a diamond pyramid indenter of 136 degrees in angle between theopposite faces to which a static load is applied, and is calculated bythe following formula.

Hardness Hv=1.854 P/d ² (kg/mm ²)≈18.1692 P/d ² (MPa)

[0114] P: load (Kg);

[0115] d: length (mm) of a diagonal line of a square recess

[0116] Also, in the invention, elasticity modulus at 20° C. of theadhesive material to be used for the adhesive roller is preferably 200kg/cm² (≈19.6 MPa) or less than that, because such material permits tosufficiently remove the foreign matter of dust and depressing imagedefects as is described above.

[0117] A second characteristic aspect of the systematizing techniques isa constitution of a thermal transfer apparatus.

[0118] A thermal transfer apparatus is used for conducting a step oftransferring the image-receiving sheet on which an image has beenprinted in the recording apparatus to a printing regular paper(hereinafter referred to as “regular paper”). This step is absolutelythe same as First Proof™. When the image-receiving sheet and the regularpaper are superimposed one over the other, and heat and pressure areapplied thereto, the two are adhered to each other. Subsequently, whenthe image-receiving film is peeled from the regular paper, only theimage and the adhesive layer remain on the proper paper, with theimage-receiving sheet support and the cushion layer being peeled off.Therefore, from the practical point of view, the image is transferredfrom the image-receiving sheet to the regular paper.

[0119] In First Proof™, the regular paper and the image-receiving sheetare superimposed one over the other on an aluminum-made guide plate andpassed between heat rollers to conduct transfer. The aluminum guideplate is used for preventing deformation of the proper paper. However,application of this system to the B2 size system of the inventionrequires an aluminum guide plate of a size larger than B2, thus therearising a problem that the apparatus requires a large space for itsinstallation. In the present system, there is employed a structurewherein the conveying path rotates 180 degrees so as to discharge on theinserting side without using the aluminum guide, and hence the space forits installation is made extremely compact (FIG. 3). However, since thealuminum guide plate was not used, there arose a problem that theregular paper was deformed. Specifically, a pair of the dischargedregular paper and the image-receiving sheet curled with theimage-receiving sheet inside, and rolled on the discharge support. It isan extremely difficult work to peel the image-receiving sheet apart fromthis rolled-up regular paper.

[0120] Thus, a technique for preventing the rolling up was devisedutilizing the bimetal effect based on the difference in the degree ofcontraction between the regular paper and the image-receiving sheet andthe ironing effect by the structure of winding around the heat roller.In the case of inserting the image-receiving sheet in the state of beingsuperimposed on the proper paper as in the conventional case, thermalcontraction of the image-receiving sheet in the inserting direction islarger than the thermal contraction of the regular paper, and hence thecurling by the bimetal effect occurs with the upper side inside. Sincethis curling direction is the same as the direction of the ironingeffect, there results a serious curling due to the synergistic effect.However, by inserting the image-receiving sheet in the state of beingdisposed under the regular paper, the direction of the curling by thebimetal effect is made downward, whereas the direction of the curling bythe ironing effect is made upward, thus the two curlings being cancelledout and the problem being solved.

[0121] The sequence of transferring the regular paper is as follows(hereinafter referred to as “method for transferring regular paper to beemployed in this system”). A thermal transfer apparatus 41 to be used inthis method and shown in FIG. 3 is to be operated manually as isdifferent from the recording apparatus.

[0122] 1) First, the temperature of a heat roller 43 (100 to 110° C.)and the conveying speed upon transfer (not shown) are set by means of adial (not shown) depending upon the kind of the regular paper 42.

[0123] 2) Next, the image-receiving sheet 20 is placed on the insertionsupport with the image facing upward, followed by removing dust on theimage by means of a destaticizing brush (not shown). A dust-free regularpaper 42 is superimposed thereon. In this occasion, the size of thesuperimposed proper paper 42 is larger than the size of the underlyingimage-receiving film 20, and hence the position of the image-receivingsheet is not seen, which makes registering difficult. In order toimprove this workability, marks 45 are provided on the insertion support44 which marks respectively show the positions of placing theimage-receiving sheet and the regular paper. The reason why the size ofthe regular paper is larger is to prevent the image-receiving sheet 20from dislocating out of the regular paper 42 to stain the heat roller 43with the image-receiving layer of the image-receiving sheet 20.

[0124] 3) When the image-receiving sheet and the regular paper areinserted in a superimposed state into the inserting inlet, an insertingrollers 46 rotates to feed the two toward a heating roller 43.

[0125] 4) When the tip of the proper plate reaches the position of theheating rollers 43, the heat rollers nip the two to initiate transfer.The heating rollers are heat-resistant silicone rubber rollers. Theimage-receiving sheet and the regular paper are adhered to each otherhere by applying thereto pressure and heat at the same time. In thedownstream of the heat rollers is provided a guide 47 made of aheat-resistant sheet, and the pair of the image-receiving sheet and theregular paper is conveyed upward between the upper heat roller and theguide 47 with the heat being applied thereto and, at the position ofpeeling claw 48, the pair is stripped from the heat roller and is guidedto the discharge outlet 50 along the guide plate 49.

[0126] 5) The pair of the image-receiving sheet and the regular paperdischarged from the discharge outlet 50 is discharged onto the insertionsupport as the two being adhered to each other. Subsequently, theimage-receiving sheet 20 is manually peeled apart from the regular paper42.

[0127] A second characteristic aspect of the systematizing techniques isa constitution of the system.

[0128] The above-described apparatuses are connected to a plate-makingsystem to exhibit functions as a color proof. As such system, it isrequired to output from the proof a printed product having an imagequality resembling that of a printed product outputted based on certainplate-making data as much as possible. Thus, a software is needed whichserves to resemble color and half-tone dots of the proof to a printedproduct. Specific examples of such connection are introduced below.

[0129] In the case of taking a proof of a printed product from aplate-making system, called Celebra™ made by Fuji Photo Film Co., Ltd.,system connection is as follows. Celebra is connected to a CTP (ComputerTo Plate) system. Final printed products can be obtained by loading aprinting plate outputted from the system on a printing machine. ToCelebra is connected the above-described recording apparatus, LuxelFINALPROOF 5600 (hereinafter also referred to as “FINALPROOF”) made byFuji Photo Film Co., Ltd. as a color proof, with a proof-drivingsoftware of PD system™ made by Fuji Photo Film Co., Ltd. interveningtherebetween for resembling color and half-tone dots to the printedproduct.

[0130] The contone (continuous tone) data converted to raster data inCelebra are in turn converted to two-value data for half-tone dots andoutputted to the CTP system, followed by final printing. On the otherhand, the same contone data are also outputted to the PD system. The PDsystem converts the received data so that the colors coincide with thatof the printed product by using at least 4 color tables. And, finally,the data are converted to two-value data for half-tone dots so as tocoincide with the half-tone dots of the printed product, and outputtedto FINALPROOF (FIG. 4).

[0131] The at least 4 color tables are previously prepared throughexperiments and stored within the system. The experiments are asfollows. An image printed via the CTP system and an image outputted onFINALPROOF via the PD system are prepared and compared with each otherwith respect to important colors, followed by comparing the measuredcolor values and preparing a table for minimizing the differences.

[0132] As has been described hereinbefore, the invention hassuccessfully realized a system constitution permitting the materialhaving a high resolving power to exhibit its full performance.

[0133] Next, the thermal transfer sheet, which is a material to be usedin the system of the invention, is described below.

[0134] It is preferred that the difference between the surface roughnessRz of the surface of the image-forming layer of the thermal transfersheet and the surface roughness Rz of the back surface layer thereof interms of the absolute value is 3.0 μm or less, and that the differencebetween the surface roughness Rz of the surface of the image-receivinglayer of the image-receiving sheet and the surface roughness Rz of theback surface layer thereof in terms of the absolute value is 3.0 μm orless. Such constitution enables to prevent image defects together withthe above-described cleaning means, prevent conveying jam and improvedot gain stability.

[0135] The term “surface roughness” as used herein in this specificationmeans a ten-point average surface roughness corresponding to Rz (maximumheight) described in JIS, and is obtained by inputting to convert anaverage value of the five height values of the highest peak to the fifthhighest peak and an average value of the five depth values of thedeepest valley to the fifth deepest valley with taking the average levelin the area selected as a standard portion from the rough surface as thestandard level. For the measurement, a needle-tough type threedimensional roughness meter (Surfcom 570A-3DF) made by Tokyo SeimitsuK.K. The measuring direction is the longitudinal direction, with acut-off value being 0.08 mm, a measuring area being 0.6 mm×0.4 mm, afeeding pitch being 0.005 mm, and a measuring speed being 0.12 mm/s.

[0136] It is more preferred in view of more enhancing theabove-described effects that the difference between the surfaceroughness Rz of the surface of the image-forming layer of the thermaltransfer sheet and the surface roughness Rz of the back surface layerthereof in terms of the absolute value is 1.0 μm or less, and that thedifference between the surface roughness Rz of the surface of theimage-receiving layer of the image-receiving sheet and the surfaceroughness Rz of the back surface layer thereof in terms of the absolutevalue is 1.0 μm or less.

[0137] Further, as another embodiment, the surface roughness of thesurface of the image-forming layer of the thermal transfer sheet andthat of the back surface layer thereof, and/or the surface roughness Rzof the surface and the back surface of the image-receiving sheet arepreferably 2 to 30 μm. Such constitution serves, together with thecleaning means, to prevent image defects, remove conveying jam andimprove dot gain stability.

[0138] Also, it is preferred that the glossiness of the image-forminglayer of the thermal transfer sheet is 80 to 99.

[0139] The glossiness greatly depends upon smoothness of the surface ofthe image-forming layer, and can influence the uniformity of thethickness of the image-forming layer. A higher glossiness provides amore uniform image-forming layer which is more suited for the use of ahighly accurate images, but a higher smoothness generates a largerresistance upon conveying, thus the two being in the trade-off relation.When the glossiness is within the range of 80 to 99, the two arecompatible and well-balanced.

[0140] Next, mechanism of forming a multi-color image by thin filmthermal transfer using a laser light is outlined below by reference toFIG. 1.

[0141] An image-receiving sheet 20 is superimposed on the surface of animage-forming layer 16 of a thermal transfer sheet 10, saidimage-forming layer 16 containing a pigment of black (K), cyan (C),magenta (M), yellow (Y) or the like to prepare a laminate 30 for formingan image. The thermal transfer sheet 10 comprises a support 12 havingprovided thereon a light-to-heat conversion layer 14 and theimage-forming layer 16 in this order, and the image-receiving sheet 20comprises a support 22 having provided thereon an image-receiving layer24. The image-receiving sheet 20 is superimposed on the thermal transfersheet 10 so that the surface of the image-forming layer 16 comes intocontact with the image-receiving layer 24 (FIG. 1(a)). When a laserlight is imagewise irradiated in time sequence from the side of thesupport 12 of the thermal transfer sheet 10, the light-to-heatconversion layer 14 of the thermal transfer sheet 10 generates heat inthe laser light-irradiated area, resulting in reduction of adhesionforce with the image-forming layer (FIG. 1(b)). Subsequently, when theimage-receiving sheet 20 is peeled apart from the thermal transfer sheet10, the laser light-irradiated area 16′ of the image-forming layer 16 istransferred onto the image-receiving layer 24 of the image-receivingsheet 20 (FIG. 1(c)).

[0142] In forming a multi-color image, the laser light to be used ispreferably a multi-beam light, particularly, a multi-beam of seconddimension arrangement. The term “multi-beam of second dimensionarrangement” as used herein means that spots of a plurality of laserbeams are in a second dimension plane arrangement wherein a plurality ofspots are arranged as rows in the main scanning direction and aplurality of spots are arranged as lines in the subsidiary scanningdirection.

[0143] Use of a laser light of multi-beam second dimension arrangementpermits to shorten the time required for laser recording.

[0144] The laser light to be used is not particularly limited, and theremay be utilized direct laser lights such as a gas laser light, e.g., anargon ion laser light, a helium neon laser light or a helium cadmiumlaser light; a solid-state laser light, e.g., a YAG laser; asemi-conductor laser; a dye laser; and an eximer laser. Alternatively,lights generated by converting to lights of a half wavelength by passingthese laser lights through a secondary high frequency element may beused as well. In the multi-color image-forming method, use of asemiconductor laser is preferred in consideration of output power andeasiness of modulation. In the multi-color image-forming method, thelaser light is irradiated preferably under such condition that the beamdiameter on the light-to-heat conversion layer is in the range of from 5to 50 μm (particularly from 6 to 30 μm), and the scanning rate ispreferably lm/sec or more (particularly 3 m/sec or more).

[0145] Also, in view of forming a multi-color image, the thickness ofthe image-forming layer in the thermal transfer sheet for black ispreferably more than the thickness of the image-forming layer in each ofthe thermal transfer sheets for yellow, magenta and cyan, and ispreferably 0.5 to 0.7 μm. Such thickness serves to depress reduction indensity due to uneven transfer upon irradiation of the black thermaltransfer sheet with a laser light.

[0146] By adjusting the thickness of the image-forming layer in thethermal transfer sheet for black to be 0.5 μm or more, an enough imagedensity is maintained with no uneven transfer, thus an image densityrequired as a proof for printing being obtained. This tendency becomesmore remarkable under a condition of a high humidity, and hence changein density due to change in environment can be depressed. On the otherhand, by adjusting the thickness to be 0.7 μm or less, an enoughtransfer sensitivity can be maintained upon laser recording, anddeposition of small dots or fine lines is also improved. This tendencybecomes more remarkable under a condition of a low humidity. Also,resolving power can be improved. The thickness of the image-forminglayer of the thermal transfer sheet for black is more preferably 0.55 to0.65 μm, particularly preferably 0.60 μm.

[0147] Further, it is preferred that the thickness of the image-forminglayer in the thermal transfer sheet for black is 0.5 to 7 μm, and thethickness of the image-forming layer in each of the thermal transfersheets for yellow, magenta and cyan is 0.2 μm or more and less than 0.5μm. By adjusting the thickness of the image-forming layer of each of thethermal transfer sheets of yellow, magenta and cyan to be 0.2 μm ormore, an enough density is maintained with forming no transferunevenness upon the laser recording whereas, by adjusting the thicknessto be less than 0.5 μm, transfer sensitivity and resolving power can beimproved. The thickness is more preferably 0.3 to 0.45 μm.

[0148] The image-forming layer in the thermal transfer sheet for blackpreferably contains carbon black. The carbon black preferably comprisesat least two kinds of carbon black products different in coloring power,because such carbon black permits to adjust reflection density withkeeping P/B (Pigment/Binder) ratio within a definite range. Coloringpower of carbon black is expressed in terms of various means. Forexample, there is illustrated PVC black degree described in JapanesePatent Laid-Open No. 140033/1998. PVC black degree is a value obtainedby adding a carbon black sample to a PVC resin, dispersing using a twinroll, forming into a sheet, and visually evaluating the black degree ofthe sample, taking the black degree of carbon black “#40” and that ofcarbon black “#45” made by Mitsubishi Chemical Co., Ltd. as scores of 1and 10, respectively, as standard values. It is possible toappropriately select two kinds or more carbon black products differentin the PVC black degree depending upon the end-use.

[0149] A process for preparing a sample is specifically described below.

[0150] [Process for Preparing a Sample]

[0151] A carbon black sample is compounded in a content of 40% by weightin an LDPE resin (Low-Density PolyEthylene) in a 250-cc Bumbury's mixer,followed by kneading at 115° C. for 4 minutes. Compounding conditions:LDPE resin 101.89 g Calcium stearate  1.39 g Irganox 1010  0.87 g carbonblack sample  69.43 g

[0152] Next, the mixture is diluted at 120° C. in a twin-roll mill to acarbon black concentration of 1% by weight. Conditions for preparing thediluted compound: LDPE resin 58.3 g Calcium stearate  0.2 g Resincontaining carbon  1.5 g black in a content of 40% by weight

[0153] The resulting compound is made into a sheet through a slit of 0.3mm in slit gap, and this sheet is cut into chips, and formed into a filmof 65±3 μm in thickness on a 240° C. hot plate.

[0154] As a method for forming a multi-color image, a number of imagelayers (image-forming layers wherein an image has been formed) may berepeatedly superimposed on the same image-receiving sheet using thethermal transfer sheets as described hereinbefore to form a multi-colorimage, or an image may once be formed on an image-receiving layer ofeach of a plurality of image-receiving sheets, followed byre-transferring onto a regular paper for printing to form a multi-colorimage.

[0155] As to the latter method, thermal transfer sheets each having animage-forming layer containing a coloring material with a different huefrom other sheet are prepared, and independent 4 or more (for example,cyan, magenta, yellow, black, red, etc.) of layered products for formingan image wherein each of the thermal transfer sheets is combined with animage-receiving sheet are prepared. Each of the layered products isirradiated with a laser light according to digital signals based on theimage through a color separation filter and, subsequently, the heattransfer sheet is peeled apart from the image-receiving sheet toindependently form a color separation image of each color on each of theimage-receiving sheets. Next, each of the color separation images thusformed is successively superimposed on a separately prepared actualsupport such as regular paper for printing or a support similar theretoto form a multi-color image.

[0156] The thermal transfer sheets to be irradiated with a laser lightare preferably those which can convert a laser beam to heat, the energyof which is utilized to form an image on an image-receiving sheet by thethin film transfer method of transferring a pigment-containingimage-forming layer onto the image-receiving sheet. The techniquesemployed for the development of an image-forming material comprising thethermal transfer sheets and an image-receiving sheet may properly beapplied to development of thermal transfer sheets and/or animage-receiving sheet based on the melt-transfer method, the abrasiontransfer method or the sublimation transfer method. The system of theinvention encompasses an image-forming materials for use in thesemethods.

[0157] The thermal transfer sheet and the image-receiving sheet aredescribed in detail below.

[0158] [Thermal Transfer Sheet]

[0159] The thermal transfer sheet comprises a support having providedthereon at least a light-to-heat conversion layer, an image-forminglayer and, if necessary, other layer or layers.

[0160] (Support)

[0161] The material for the support of the thermal transfer sheet is notparticularly limited, and various materials for the support may be useddepending upon the end-use. As the support, those which have a gooddimensional stability and can resist heat upon image formation arepreferred. As the preferred examples of the material for the support,there are illustrated synthetic resin materials such as polyethyleneterephthalate, polyethylene 2,6-naphthalate, polycarbonate, polymethylmethacrylate, polyethylene, polypropylene, polyvinyl chloride,polyvinylidene chloride, polystyrene, styrene-acrylonitrile copolymer,polyamide (aromatic or aliphatic), polyimide, polyamidimide,polysulfone, etc. Among them, biaxially oriented polyethyleneterephthalate is preferred in consideration of mechanical strength ordimensional stability for heat. Additionally, in the case of using forpreparing a color proof utilizing the laser recording, the support forthe thermal transfer sheet is preferably formed from a transparentsynthetic resin material which can transmit a laser light. The thicknessof the support is preferably 25 to 130 μm, particularly preferably 50 to120 μm. The center-line average surface roughness Ra (measured based onJIS B0601 using, for example, Surfcom made by Tokyo Seimitsu K.K.) ofthe support on the image-forming layer side is preferably less than 0.1μm. The Young's modulus of the support in the longitudinal direction ispreferably 200 to 1200 Kg/mm² (≈0.2 to 12 GPa), and the young's modulusin the transverse direction is preferably 250 to 1600 Kg/mm² (≈2.5 to 16GPa). The F-5 value of the support in the longitudinal direction ispreferably 5 to 50 Kg/mm² (≈49 to 490 MPa), and the F-5 value of thesupport in the transverse direction is preferably 3 to 30 Kg/mm² (≈29.4to 294 MPa). The F-5 value of the support in the longitudinal directionis generally higher than the F-5 value of the support in the transversedirection, though not being limited so in the case where the strength inthe transverse direction is required to be higher. The heat-shrinkingratio of the support in the longitudinal direction and the transversedirection at 100° C. for 30 minutes is preferably 3% or less, morepreferably 1.5% or less, and the heat-shrinking ratio at 80° C. for 30minutes is preferably 1% or less, more preferably 0.5% or less. Thebreaking strength in both directions is preferably 5 to 100 Kg/mm2(=0.49 to 980 MPa), and the elasticity modulus is preferably 100 to 2000Kg/mm2 (≈0.98 to 19.6 GPa).

[0162] In order to improve adhesion to the light-to-heat conversionlayer to be provided on the support of the thermal transfer sheet, thesupport may be subjected to a surface-activating treatment, and/or one,two or more undercoating layers may be provided on the support. Examplesof the surface-activating treatment include a glow discharge treatmentand a corona discharge treatment. As the material for the undercoatinglayer, those which show high adhesion properties to both the surface ofthe support and the surface of the light-to-heat conversion layer, andwhich have a small heat conductivity and an excellent heat resistanceare preferred. Examples of such materials for the undercoating layerinclude styrene, styrene-butadiene copolymer and gelatin. The thicknessof the whole undercoating layers is usually 0.01 to 2 μm. Also, on thesurface opposite to the side on which the light-to-heat conversion layerof the thermal transfer sheet is provided may be provided, as needed,various functional layers such as an anti-reflecting layer or anantistatic layer, or the surface may be subjected to surface treatment.

[0163] (Backing Layer)

[0164] It is preferred to provide a backing layer on the surfaceopposite to the side on which the light-to-heat conversion layer of thethermal transfer sheet of the invention is provided. The backing layeris preferably constituted by a first backing layer provided adjacent tothe support and a second backing layer provided on the opposite side ofthis first backing layer to the support. In the invention, the ratio ofthe weight A of an antistatic agent contained in the first backing layerto the weight B of an antistatic agent contained in the second backinglayer, B/A, is preferably less than 0.3. In case when B/A is 0.3 ormore, there results a tendency of the sliding properties and dustdropping of the backing layer becoming serious.

[0165] The thickness of the first backing layer, C, is preferably 0.01to 1 μm, more preferably 0.01 to 0.2 μm. Also, the thickness of thesecond backing layer, D, is preferably 0.01 to 1 μm, more preferably0.01 to 0.2 μm. The ratio of the thickness of the first backing layerand the thickness of the second backing layer, C:D, is preferably 1:2 to5:1.

[0166] As the antistatic agents to be used in the first and the secondbacking layers, there may be used nonionic surfactants such aspolyoxyethylenealkylamine and glycerin fatty acid ester, cationicsurfactants such as quaternary ammonium salt, anionic surfactants suchas alkylphosphate, amphoteric surfactants and electroconductive resins.

[0167] Also, conductive fine particles may be used as the antistaticagent. Examples of such conductive fine particles include oxides such asZnO, TiO₂, SnO₂, Al₂O₃, In₂O₃, MgO, BaO, CoO, CuO, Cu₂O, CaO, SrO, BaO₂,PbO, PbO₂, MnO₃, MoO₃, SiO₂, ZrO₂, Ag₂O, Y₂O₃, Bi₂O₃, Ti₂O₃, Sb₂O₃,Sb₂O₅, K₂Ti₆ 013, NaCaP₂O₁₈ and MgB₂O₅; sulfides such as CuS and ZnS;carbides such as SiC, TiC, ZrC, VC, NbC, MoC and WC; nitrides such asSi₃N₄, TiN, ZrN, VN, NbN and Cr₂N; borides such as TiB₂, ZrB₂, NbB₂,TaB₂, CrB, MoB, WB and LaB₅; silicides such as TiSi₂, ZrSi₂, NbSi₂,TaSi₂, CrSi₂, MoSi₂ and WSi₂; metal salts such as BaCO₃, CaCO₃, SrCO₃,BaSO₄ and CaSO₄; and composites such as SiN₄—SiC and 9Al₂O₃—2B₂O₃. Thesemay be used independently or in combination of two or more of them. Ofthese, SnO₂, ZnO, Al₂O₃, TiO₂, In₂O₃, MgO, BaO and MoO₃ are preferred,with SnO₂, ZnO, In₂O₃ and TiO₂ being more preferred, and SnO₂ beingparticularly preferred.

[0168] Additionally, in the case of using the thermal transfer materialof the invention for the laser thermal transfer recording system, theantistatic agent to be used in the backing layer is preferablysubstantially transparent so as to permit transmission of a laser light.

[0169] In the case of using the conductive metal oxide as an antistaticagent, the smaller the particle size thereof, the more preferred, forthe purpose of minimizing scattering of the laser light. However, theparticle size should be determined using the ratio of refractive indexof the particles to that of the binder as a parameter. In general, theaverage particle size is in the range of from 0.001 to 0.5 μm,preferably from 0.003 to 0.2 μm. The term “average particle size” asused herein means the value for not only the particle size of primaryparticles of the conductive metal oxide but the particle size of higherstructure particles.

[0170] To the first and the second backing layers may be added variousadditives such as a surfactant, a slipping agent and a matting agent anda binder in addition to the antistatic agent. The amount of theantistatic agent to be incorporated in the first backing layer ispreferably 10 to 1000 parts by weight, more preferably 200 to 800 partsby weight, per 100 parts by weight of the binder. Also, the amount ofthe antistatic agent to be contained in the second backing layer ispreferably 0 to 300 parts by weight, more preferably 0 to 100 parts byweight, per 100 parts by weight of the binder.

[0171] As the binder to be used for forming the first and the secondbacking layers, there may be illustrated, for example, homopolymers andcopolymers of acrylic monomers such as acrylic acid, methacrylic acid,an acrylic ester and an methacrylic ester; cellulose series polymerssuch as nitrocellulose, methyl cellulose, ethyl cellulose and celluloseacetate; polyvinyl polymers and copolymers of a vinyl compound such aspolyethylene, polypropylene, polystyrene, a vinyl chloride copolymer, avinyl chloride-vinyl acetate copolymer, polyvinylpyrrolidone, polyvinylbutyral and polyvinyl alcohol; condensation polymers such as apolyester, a polyurethane and a polyamide; rubber type thermoplasticpolymers such as a butadiene-styrene copolymer; polymers obtained bypolymerizing and cross-linking a photo-polymerizable orthermo-polymerizable compound such as an epoxy compound; and a melaminecompound.

[0172] (Light-to-Heat Conversion Layer)

[0173] The light-to-heat conversion layer contains a light-to-heatconverting substance, a binder and, if necessary, a matting agent and,further, other ingredients.

[0174] The light-to-heat converting substance is a substance which has afunction of converting the irradiated light energy to a heat energy. Ingeneral, it is a coloring material (including a pigment; hereinafter thesame) which can absorb a laser light. In the case of conducting imagerecording by an infrared ray laser, it is preferred to use an infraredray-absorbing coloring material as the light-to-heat convertingsubstance. Examples of the coloring material include black pigments suchas carbon black; pigments of large ring compounds showing an absorptionin the range of from the visible region to near-infrared region such asphthalocyanine and naphthalocyanine; organic dyes (such as cyanine dyes,e.g., indolenine dyes; anthraquinone series dyes; azulene series dyes;and phthalocyanine dyes) used as a laser light-absorbing substance forhigh-density laser recording such as photo-discs; and organometalliccompound coloring materials such as a dithiol-nickel complex.Especially, the cyanine series coloring materials are preferred, sincethey show such a high absorbancy index for a light of infrared regionthat, when used as a light-to-heat converting substance, they serve toreduce the thickness of the light-to-heat conversion layer, leading tomore improving the recording sensitivity of the thermal transfer sheet.

[0175] As the light-to-heat converting substance, inorganic substancessuch as particulate metal substances such as blackened silver may beused other than the coloring materials.

[0176] As a binder to be contained in the light-to-heat conversionlayer, those resins are preferred which have a strength of at leastforming a layer on a support and have a high thermal conductivity.Further, those resins which are heat-resistance and are not decomposedeven by heat generated from the light-to-heat converting substance uponimage recording are preferred because, even when the light irradiationis conducted with a high energy, the light-to-heat conversion layer canmaintain the smoothness of its surface after irradiation with a light.Specifically, those resins are preferred which show a thermaldecomposition temperature (a temperature at which the resin loses 5%weight thereof in an air stream at a temperature-raising rate of 10C/min according to TGA (thermogravimetric analysis) method) of 400° C.or higher, more preferably 500° C. or higher. Also, the binder has aglass transition temperature of preferably 200 to 400° C., morepreferably 250 to 350° C. In case where the glass transition temperatureis lower than 200° C., the resulting image can generate fog in somecases whereas, in case where higher than 400° C., solubility of theresin is so reduced that, in some cases, production efficiency islowered.

[0177] Additionally, heat resistance of the binder for the light-to-heatconversion layer (for example, heat deformation temperature or thermaldecomposition temperature) is preferably higher than that of thosematerials to be used for other layers to be provided on thelight-to-heat conversion layer.

[0178] Specifically, there are illustrated acrylic acid-based resinssuch as polymethyl methacrylate; polycarbonate; polystyrene; vinylresins such as vinyl chloride/vinyl acetate copolymer and polyvinylalcohol; polyvinyl butyral; polyester; polyvinyl chloride; polyamide;polyimide; polyetherimide; polysulfone; polyether sulfone; aramide;polyurethane; epoxy resin; and urea/melamine resin. Of these, thepolyimide resin is preferred.

[0179] Particularly, the polyimide resins represented by the followinggeneral formulae (I) to (VII) are preferred, because they are soluble inan organic solvent, and use of these polyimide resins serves to improveproductivity of the thermal transfer sheets. Also, they are preferred inthe point that they improve viscosity stability, long-timepreservability and humidity resistance of a coating solution for thelight-to-heat conversion layer.

[0180] In the above general formulae (I) and (II), Ar represents anaromatic group represented by the following structural formulae (1) to(3), and n represents an integer of 10 to 100.

[0181] In the above general formulae (III) and (IV), Ar² represents anaromatic group represented by the following structural formulae (4) to(7), and n represents an integer of 10 to 100.

[0182] In the above general formulae (V) to (VII), n and m eachrepresents an integer of 10 to 100. In the formula (VI), the ratio ofn:m is 6:4 to 9:1.

[0183] Additionally, as a standard for judging whether a resin issoluble in an organic solvent or not, the resin is judged to be solublein an organic solvent when 10 parts by weight or more of the resin issoluble in 100 parts by weight of N-methylpyrrolidone. A resin which issoluble in an amount of 10 parts by weight or more is preferably used asa resin for the light-to-heat conversion layer. Amore preferred resin isthat which is soluble in an amount of 100 parts by weight or more in 100parts by weight of N-methylpyrrolidone.

[0184] As a matting agent to be contained in the light-to-heatconversion layer, there may be illustrated inorganic fine particles andorganic fine particles. Examples of the inorganic particles includesilica, titanium oxide, aluminum oxide, zinc oxide, magnesium oxide,metal salts such as barium sulfate, magnesium sulfate, aluminumhydroxide, magnesium hydroxide, boron nitride, etc., kaolin, clay, talc,zinc flower, lead white, zeeklite, quarts, diatomaceous earth, barlite,bentonite, mica, synthetic mica, etc. Examples of the organic fineparticles include resin particles such as fluorine-containing resinparticles, guanamine resin particles, acryl resin particles,styrene-acryl copolymer resin particles, silicone resin particles,melamine resin particles, epoxy resin particles, etc.

[0185] The particle size of the matting agent is usually 0.3 to 30 μm,preferably 0.5 to 20 μm, and the amount thereof is preferably 0.1 to 100mg/m².

[0186] To the light-to-heat conversion layer may further be added, asneeded, a surfactant, a thickening agent, an antistatic agent, etc.

[0187] The light-to-heat conversion layer can be provided by dissolvinga light-to-heat converting substance and a binder and, if necessary, amatting agent and other ingredients to prepare a coating solution, andcoating it on a support, followed by drying. Examples of the organicsolvent for dissolving a polyimide resin include n-hexane, cyclohexane,diglyme, xylene, toluene, ethyl acetate, tetrahydrofuran, methyl ethylketone, acetone, cyclohexanone, 1,4-dioxane, 1,3-dioxane, dimethylacetate, N-methyl-2-pyrrolidone, dimethylsulfoxide, dimethylformamide,dimethylacetamide, γ-butyrolactone, ethanol, methanol, etc. The coatingand drying procedures are preferably conducted by utilizing commoncoating and drying methods. In the case of using polyethyleneterephthalate as a support, it is preferred to conduct drying at atemperature of 80 to 150° C.

[0188] When the amount of the binder in the light-to-heat conversionlayer is too small, cohesive force of the light-to-heat conversion layerdecreases and, when a formed image is transferred to the image-receivingsheet, the light-to-heat conversion layer is liable to be transferredthereto as well, thus causing color mixing of the image. Also, when theamount of the polyimide resin is too much, the light-to-heat conversionlayer needs to be made thicker in order to achieve a necessary definitelight absorption ratio. This is liable to cause a deterioration ofsensitivity. The solid component ratio by weight of the light-to-heatconverting substance and the binder in the light-to-heat conversionlayer is preferably 1:20 to 2:1, more preferably 1:10 to 2:1.

[0189] Also, reduction in thickness of the light-to-heat conversionlayer enables to make the thermal transfer sheet more sensitive, thusbeing preferred. The thickness of the light-to-heat conversion layer ispreferably 0.03 to 1.0 μm, more preferably 0.05 to 0.5 μm. Also, whenthe light-to-heat conversion layer shows an optical density of 0.80 to1.26 for a light of 808 nm in wavelength, it can improve transfersensitivity of the image-forming layer, thus being preferred. Alight-to-heat conversion layer showing the optical density of 0.92 to1.15 for the light of the above-described wavelength is more preferred.In case when the optical density in the laser peak wave length is lessthan 0.80, it becomes insufficient to convert the irradiated light toheat and, in some cases, there results a reduced transfer sensitivity.On the other hand, when exceeding 1.26, functions of the light-to-heatconversion layer are affected to generate fog in some cases.

[0190] (Image-Forming Layer)

[0191] The image-forming layer contains at least a pigment to betransferred to the image-receiving layer to form an image, and furthercontains a binder for forming a layer and, if necessary, othercomponents.

[0192] The pigments are generally roughly grouped into organic pigmentsand inorganic pigments. The former are particularly excellent intransparency of the coating film, whereas the latter are generallyexcellent in opacifying power, and hence it suffices to select a properone depending upon the use. In the case of using the thermal transfersheet for proofing printed colors, organic pigments are preferably usedwhich have the same color tones as commonly used colors such as yellow,magenta, cyan, black, red, green, blue, orange, etc. or have a colorsimilar thereto. In addition, in some cases, there may be used metalpowders and fluorescent pigments. Examples of the pigments to bepreferably used include azo pigments, phthalocyanine pigments,anthraquinone pigments, dioxazine pigments, quinacridone pigments,isoindolinone pigments and nitro pigments. Pigments to be used in theimage-forming layer are illustrated below according to hue, which,however, are not limitative at all.

[0193] 1) Yellow Pigments:

[0194] Pigment Yellow 12 (C.I. No. 21090)

[0195] Examples) Permanent Yellow DHG (made by Clariant Japan K.K.),Lionol Yellow 1212B (made by Toyo Ink Mfg. Co., Ltd.),

[0196] Irgalite Yellow LCT (made by Ciba Specialty Chemicals, Ltd.),Symuler Fast Yellow GTF 219 (made by Dai-Nippon Ink & Chemicals, Inc.)

[0197] Pigment Yellow 13 (C.I. No. 21100)

[0198] Examples) Permanent Yellow GR (made by Clariant Japan K.K.),Lionol Yellow 1313 (made by Toyo Ink Mfg. Co., Ltd.)

[0199] Pigment Yellow 14 (C.I. No. 21095)

[0200] Examples) Permanent Yellow G (made by Clariant Japan K.K.),Lionol Yellow 1401-G (made by Toyo Ink Mfg. Co., Ltd.),

[0201] Seika Fast Yellow 2270 (made by Dainichi Seika Kogyo K.K.),Symuler Fast Yellow 4400 (made by Dai-nippon Ink & Chemicals, Inc.

[0202] Pigment Yellow 17 (C.I. No. 21105)

[0203] Examples) Permanent Yellow GG02 (made by Clariant Japan K.K.),Symuler Fast Yellow 8GF (made by Dai-nippon Ink & Chemicals, Inc.

[0204] Pigment Yellow 155

[0205] Examples) Graphtol Yellow 3GP (made by Clariant Japan K.K.)

[0206] Pigment Yellow 180 (C.I. No. 21290)

[0207] Examples) Novoperm Yellow P-HG (made by Clariant Japan K.K.) PVFast Yellow HG (made by Clariant Japan K.K.)

[0208] Pigment Yellow 139 (C.I. No. 56298)

[0209] Examples) Novoperm Yellow M2R 70 (made by Clariant Japan K.K.)

[0210] 2) Magenta Pigments

[0211] Pigment Red 57:1 (C.I. No. 15850:1)

[0212] Examples) Graphtol Rubine L6B (made by Clariant Japan K.K.),Lionol Red 6B-4290G (made by Toyo Ink Mfg. Co., Ltd.), Irgalite Rubine4BL (Ciba Specialty Chemicals K.K.), Symuler Brilliant Carmine 6B-229(made by Dai-nippon Ink & Chemicals, Inc.)

[0213] Pigment Red 122 (C.I. No. 73915)

[0214] Examples) Hosterperm Pink E (made by Clariant Japan K.K.),Lionogen Magenta 5790 (made by Toyo Ink mfg. Co., Ltd.), Fastogen SuperMagenta RH (made by Dai-nippon Ink & Chemicals, Inc.)

[0215] Pigment Red 53:1 (C.I. No. 15585:1)

[0216] Examples) Permanent Lake Red LCY (made by Clariant Japan K.K.),Symuler Lake Red C conc (made by Dai-nippon Ink & Chemicals, Inc.)

[0217] Pigment Red 48:2 (C.I. No. 15865:2)

[0218] Examples) Permanent Red W2T (made by Clariant Japan K.K.), LionolRed LX235 (made by Toyo Ink Mfg. Co., Ltd.), Symuler Red 3012 (made byDai-nippon Ink & Chemicals, Inc.)

[0219] Pigment Red 177 (C.I. No. 65300)

[0220] Examples) Cromophtal Red A2B (made by Ciba Specialty ChemicalsK.K.)

[0221] 3) Cyan Pigments

[0222] Pigment Blue 15 (C.I. No. 74160)

[0223] Examples) Lionol Blue 7027 (made by Toyo Ink Mfg. Co., Ltd.)Fastogen Blue BB (made by Dai-nippon Ink & Chemicals, Inc.)

[0224] Pigment Blue 15:1 (C.I. No. 74160)

[0225] Examples) Hosterperm Blue A2R (made by Clariant Japan K.K.),Fastogen Blue 5050 (made by Dai-nippon Ink & Chemicals, Inc.)

[0226] Pigment Blue 15:2 (C.I. No. 74160)

[0227] Examples) Hosterperm Blue AFL (made by Clariant Japan K.K.),Irgalite Blue BSP (made by Ciba Specialty Chemicals K.K.), Fastogen BlueGP (made by Dai-nippon Ink & Chemicals, Inc.)

[0228] Pigment Blue 15:3 (C.I. No. 74160)

[0229] Examples) Hosterperm Blue B2G (made by Clariant Japan K.K.),Lionol Blue FG7330 (made by Toyo Ink Mfg. Co., Ltd.), Cromophtal Blue4GNP (Ciba Specialty Chemicals K.K.), Fastogen Blue FGF (Dai-nippon Ink& Chemicals, Inc.)

[0230] Pigment Blue 15:4 (C.I. No. 74160)

[0231] Examples) Hosterperm Blue BFL (Clariant Japan K.K.), Cyanine Blue700-10FG (made by Toyo Ink Mfg. Co., Ltd.), Irgalite Blue GLNF (made byCiba Specialty Chemicals K.K.), Gastogen Blue FGS (Dai-nippon Ink &Chemicals, Inc.)

[0232] 4) Black Pigments

[0233] Pigment Black 7 (carbon black C.I. No. 77266) Examples)Mitsubishi Carbon Black MA100 (made by Mitsubishi Chemical Co., Ltd.),Mitsubishi Carbon Black #5 (made by Mitsubishi Chemical Co., Ltd.),Black Pearls 430 (made by Cabot Co.)

[0234] 5) Red Pigments

[0235] Pigment Red 48:1 (C.I. No. 15865:1)

[0236] Examples) Lionol Red 2B-FG3300 (made by Toyo Ink Mfg. Co., Ltd.),Symuler Red NRY, Symuler Red 3108 (made by Dai-nippon Ink & Chemicals,Inc.)

[0237] Pigment Red 48:3 (C.I. No. 15865:3)

[0238] Examples) Permanent Red 3RL (made by Clariant Japan K.K.),Symuler Red 2BS (made by Dai-nippon Ink & Chemicals, Inc.)

[0239] 6) Blue Pigments

[0240] Pigment Blue 15:6 (C.I. No. 74160)

[0241] Example) Lionol Blue ES (Toyo Ink Mfg. Co., Ltd.)

[0242] Pigment Blue 60 (C.I. No. 69800)

[0243] Examples) Hosterperm Blue RL01 (made by Clariant Japan K.K.),Lionolgen Blue 6501 (made by Toyo Ink Mfg. Co., Ltd.)

[0244] 7) Green Pigments

[0245] Pigment Green 7 (C.I. No. 74260) Example) Fastogen Green S (madeby Dai-nippon Ink & Chemicals, Inc.)

[0246] 8) Orange Pigments

[0247] Pigment Orange 43 (C.I. No. 71105) Example) Hosterperm Orange GR(made by Clariant Japan K.K.)

[0248] Also, as pigments to be used in the invention, proper productsmay be selected by reference to “GanryoBinran” compiled by Nihon GanryoGijutsu Kyokai, and published by Seibundo Sinkosha in 1989, “COLORINDEX, THE SOCIETY OF DYES & COLOURIST, THIRD EDITION, 1987”, etc.

[0249] The average particle size of the pigments is preferably 0.03 to 1μm, more preferably 0.05 to 0.5 μm.

[0250] Particles having a particle size of 0.03 μm or larger do notrequire a higher dispersing cost and do not cause gelation of aresulting dispersion, whereas particles having a particle size of 1 μmor smaller provide a good adhesion between the image-forming layer andthe image-receiving layer owing to the absence of coarse particles andcan improve transparency of the image-forming layer.

[0251] As the binder for the image-forming layer, amorphous organic highmolecular polymers of 40 to 150° C. in softening point are preferred. Asthe amorphous organic high molecular polymers, there may be used, forexample, a butyral resin, a polyamide resin, a polyethylene imine resin,a sulfonamide resin, a polyester polyol resin, a petroleum resin,homopolymers or copolymers of styrene, its derivative or substitutedstyrene such as styrene, vinyltoluene, α-methylstyrene, 2-methylstyrene,chlorostyrene, vinylbenzoic acid, sodium vinylbenzoate or aminostyrene,homopolymers of vinyl monomers such as methacrylates (e.g., methylmethacrylate, ethyl methacrylate, butyl methacrylate and hydroxyethylmethacrylate), methacrylic acid, acrylates (e.g., methyl acrylate, ethylacrylate, butyl acrylate and α-ethylhexyl acrylate), acrylic acid,dienes such as butadiene and isoprene, acrylonitrile, vinyl ethers,maleic acid and maleic acid ester, maleic anhydride, cinnamic acid,vinyl chloride and vinyl acetate or copolymers thereof with othermonomers. These resins may be used as a mixture of two or more of them.

[0252] The image-forming layer contains the pigment in an amount ofpreferably 30 to 70% by weight, more preferably 30 to 50% by weight.Also, the image-forming layer contains the resin in an amount ofpreferably 70 to 30% by weight, more preferably 70 to 40% by weight.

[0253] The image-forming layer may contain the following ingredients (1)to (3) as the aforesaid other ingredients.

[0254] (1) Waxes

[0255] Waxes include mineral waxes, natural waxes and synthetic waxes.Examples of the mineral waxes include petroleum waxes such s paraffinwax, microcrystalline wax, ester wax, oxidized wax, etc., montan wax,ozokerite, ceresin and the like. Among these, paraffin wax is preferred.The paraffin wax is a product separated from petroleum and, dependingupon melting point, various kinds of paraffin waxes are commerciallyavailable.

[0256] Examples of the natural waxes include vegetable waxes such ascarnauba wax, Japan wax, ouricury wax, and espal wax and animal waxessuch as beeswax, insect wax, shellac wax and spermaceti.

[0257] The synthetic waxes are used generally as lubricants, and areusually composed of higher fatty acid compounds. Examples of suchsynthetic waxes include the following:

[0258] 1) Fatty Acid-Based Waxes

[0259] Straight-chain saturated fatty acids represented by the followinggeneral formula:

CH₃(CH₂)_(n)NCOOH

[0260] wherein n represents an integer of 6 to 28 are illustrated.Specific examples thereof include stearic acid, behenic acid, palmiticacid, 12-hydroxystearic acid, azelaic acid, etc.

[0261] Also, there are illustrated metal salts (e.g., K, Ca, Zn, Mg,etc.) of the above-described fatty acids.

[0262] 2) Fatty Acid Ester-Based Waxes

[0263] Specific examples of the fatty acid esters include ethylstearate, lauryl stearate, ethyl behenate, hexyl behenate, behenylmyristate, etc.

[0264] 3) Fatty Acid Amide-Based Waxes

[0265] Examples of the fatty acid amides include stearic amide, lauricamide, etc.

[0266] 4) Aliphatic Alcohol-Based Waxes

[0267] Straight-chain saturated aliphatic alcohols represented by thefollowing general formula:

CH₃(CH₂)_(n)OH

[0268] wherein n represents an integer of 6 to 28 are illustrated.Specific examples thereof include stearyl alcohol, etc.

[0269] Among the synthetic waxes described in 1) to 4) above, higherfatty acid amides such as stearic amide and lauric amide areparticularly suitable. Additionally, the above-mentioned wax compoundsmay be used singly or in a suitable combination thereof as required.

[0270] (2) Plasticizer

[0271] The plasticizer is preferably an ester compound, and mention canbe made of known plasticizer, for example, phthalates such as dibutylphthalate, di-n-octyl phthalate, di(2-ethylhexyl) phthalate, dinonylphthalate, dilauryl phthalate, butyl lauryl phthalate and butyl benzylphthalate; aliphatic dibasic acid esters such as di(2-ethylhexyl)adipate and di(2-ethylhexyl) sebacate; phosphoric acid triesters such astricresyl phosphate and tri(2-ethylhexyl) phosphate; polyol polyesterssuch as polyethylene glycol; epoxy compounds such as epoxy fatty acidester; and the like. Of these, esters of vinyl monomers, particularlyesters of acrylic acid or methacrylic acid, are preferred in respect ofimprovement of transfer sensitivity and alleviating transfer unevenness,and of greater effect of regulating breaking elongation.

[0272] Examples of the acrylic or methacrylic ester compounds includepolyethylene glycol dimethacrylate, 1,2,4-butanetriol trimethacrylate,trimethylolethane triacrylate, pentaerythritol acrylate, pentaerythritoltetraacrylate, dipentaerythritol polyacrylate, etc.

[0273] Also, the plasticizers may be high polymers, among whichpolyesters are preferred in respect of greater effect by the additionand resistance to diffusion under storage conditions. Examples of thepolyesters include sebacic acid-based polyesters and adipic acid-basedpolyesters.

[0274] Additionally, the additives to be contained in the image-forminglayer are not limited to these. Also, the plasticizers may be used aloneor in combination of two or more of them.

[0275] In case when the content of the additives in the image-forminglayer is too high, resolution of the transfer image may be lowered, filmstrength of the image-forming layer itself maybe lowered, and transferto the image-receiving sheet may occur at non-irradiated portions due toa reduction in adhesion between the light-to-heat conversion layer andthe image-forming layer. In view of the foregoing, the content of thewax is preferably 0.1 to 30% by weight, more preferably 1 to 20% byweight, based on the total solid content of the image-forming layer.Also, the content of the plasticizer is preferably 0.1 to 20% by weight,more preferably 0.1 to 10% by weight, based on the total solid contentof the image-forming layer.

[0276] (3) Others

[0277] The image-forming layer may further contain surfactants,inorganic or organic fine particles (metal powder, silica gel, etc.),oils (linseed oil, mineral oil, etc.), thickening agents, antistaticagents, etc. in addition to the components described above. Except forcases where a black image is to be obtained, the energy necessary fortransfer can be reduced by incorporation of a material that absorbs atthe wavelength of a light source to be used for recording an image. Thematerial that absorbs at the wavelength of the light source may be apigment or a dye. In the case of obtaining a color image, it ispreferred in view of color reproduction that an infrared light sourcesuch as a semiconductor laser or the like is used for recording theimage, and a dye having considerable absorption at the wavelength of thelight source and less absorption in the visible region is used as thematerial. Examples of near infrared dyes include compounds described inJapanese Patent Laid-Open No. 103476/1991.

[0278] The image-forming layer can be provided by preparing a coatingsolution containing dissolved or dispersed therein the pigment, thebinder and the like, coating it on the light-to-heat conversion layer(or, in the case where a heat-sensitive release layer is provided on thelight-to-heat conversion layer, coating the coating solution on theheat-sensitive release layer), and drying. Examples of a solvent to beused for preparing the coating solution include n-propyl alcohol, methylethyl ketone, propylene glycol monomethyl ether (MFG), methanol, water,etc. The coating and drying can be conducted utilizing a common coatingand drying method.

[0279] It is possible to provide, on the light-to-heat conversion layerof the thermal transfer sheet, a heat-sensitive release layer containinga heat-sensitive material which generates gas or releases adhesion waterby the action of heat generated in the light-to-heat conversion layer,and which thus weakens the adhesion force between the light-to-heatconversion layer and the image-forming layer. As the heat-sensitivematerials, there may be used a compound (a polymer or a low molecularcompound) which itself is decomposed or denatured by heat to generate agas, a compound (a polymer or a low molecular compound) which hasabsorbed or adsorbed a large amount of an easily vaporizing gas such asmoisture, and the like. These may be used in combination.

[0280] Examples of the polymer capable of generating a gas upon beingdecomposed or denatured include: auto-oxidizable polymers such asnitrocellulose; halogen-containing polymers such as chlorinatedpolyolefin, chlorinated rubber, polychlorinated rubber, polyvinylidenechloride, etc.; acrylic polymers such as polyisobutyl methacrylate, onwhich a volatile compound such as water is adsorbed; cellulose esterssuch as ethyl cellulose, on which a volatile compound such as water isadsorbed; and natural high polymer compounds such as gelatin, on which avolatile compound such as water is adsorbed. Examples of the lowmolecular compound capable of generating a gas upon being decomposed ordenatured include compounds such as diazo compounds and azide compoundswhich can be decomposed by heat to generate a gas.

[0281] Additionally, such decomposition or denaturing of theheat-sensitive material by heat occurs at a temperature of preferably280° C. or lower, particularly preferably 230 C or lower.

[0282] In a case where a low molecular compound is used as theheat-sensitive material, it is desirable that the low molecular compoundis used in combination with a binder. As the binder, the above-mentionedpolymer which itself is decomposed or denatured by heat to generate agas may be used. Also, those ordinary binders which do not have suchcharacteristics may be used. In the case of using the heat-sensitive lowmolecular compound and the binder in combination, the weight ratio ofthe former to the latter is preferably in a range of 0.02:1 to 3:1, morepreferably 0.05:1 to 2:1. The heat-sensitive release layer preferablycovers almost all over the surface of the light-to-heat conversionlayer, and has a thickness of generally 0.03 to 1 μm, preferably 0.05 to0.5 μm.

[0283] With a thermal transfer sheet which comprises a support havingprovided thereon the light-to-heat conversion layer, the heat-sensitiverelease layer and the image-forming layer in this order, thelight-sensitive release layer is decomposed or denatured by heatconducted from the light-to-heat conversion layer to thereby generate agas. Then, due to this decomposition or generation of a gas, a portionof the heat-sensitive peeling layer disappears or cohesive failure takesplace within the heat-sensitive release layer, thus binding forcebetween the light-to-heat conversion layer and the image-forming layerbeing reduced. Hence, because of this behavior of the heat-sensitiverelease layer, a portion of the heat-sensitive release layer may adhereto the image-forming layer and may appear on the surface of the finallyformed image, thus causing color mixing of the image. Therefore, it isdesirable that the heat-sensitive release layer is almost non-colored,i.e., that the heat-sensitive release layer exhibits a high permeabilityfor visible light to prevent the appearance of color mixing on the imageto be formed even when such image transfer as described above of theheat-sensitive release layer takes place. Specifically, the lightabsorption coefficient of the heat-sensitive release layer is preferably50% or less, more preferably 10% or less.

[0284] Additionally, instead of the heat-sensitive release layer beingprovided separately, the light-to-heat conversion layer can be used asthe heat-sensitive release layer by adding the aforementionedheat-sensitive material to the light-to-heat conversion layer-formingcoating solution, thus making the light-to-heat conversion layer toserve as both the light-to-heat conversion layer and the heat-sensitivelayer.

[0285] It is preferred to adjust the static friction coefficient of theoutermost layer of the thermal transfer sheet on the image-forminglayer-coated side to be 0.35 or less, preferably 0.20 or less. Byadjusting the static friction coefficient to be 0.35 or less, roll stainof the thermal transfer sheet upon conveyance can be prevented, andthere can be obtained an image with a high image quality. The staticfriction coefficient is measured according to the method described inJapanese Patent Application No. 85759/2000, paragraph (0011).

[0286] The smoothster value of the surface of the image-forming layer at23° C. and 55% RH is preferably 0.5 to 50 mmHg (≈0.0665 to 6.65 kPa),and Ra thereof is preferably 0.05 to 0.4 μm. Such surface is preferredin respect of transfer and image quality because it can minimizemicroscopic air gaps which prevent the image-receiving layer and theimage-forming layer from contacting with each other. The Ra value can bemeasured according to JIS B0601 using a surface roughness meter(Surfcom; made by Tokyo Seiki K.K.). The surface hardness of theimage-forming layer is preferably 10 g or more measured by using asapphire needle. The electrostatic charge potential of the image-forminglayer generated by electrostatically charging the thermal transfer sheetaccording to the test standard of US government 4046 and earthing forone second is preferably 100 to 100 V. The surface resistance of theimage-forming layer at 23° C. and 55% RH is preferably 10⁹ Ω or less.

[0287] Next, the image-receiving sheet to be used in combination withthe thermal transfer sheet is described below.

[0288] [Image-Receiving Sheet]

[0289] (Stratum Structure)

[0290] The image-receiving sheet usually comprises a support havingprovided thereon one or more image-receiving layers and, if necessary,one or more of a cushion layer, a release layer and an intermediatelayer between the support and the image-receiving layer. Also, toprovide a backing layer on the opposite side of the support to the sideon which the image-receiving layer is provided is preferred in respectof conveyance.

[0291] (Support)

[0292] As a support, there are illustrated common sheet-like substratematerials such as a plastic sheet, a metal sheet, a glass sheet, aresin-coated paper, paper and various composite materials. Examples ofthe plastic sheet include a polyethylene terephthalate sheet, apolycarbonate sheet, a polyethylene sheet, a polyvinyl chloride sheet, apolyvinylidene chloride sheet, a polystyrene sheet, astyrene-acrylonitrile sheet and a polyester sheet. Also, examples of thepaper include regular printing paper and coated paper.

[0293] Presence of fine voids in the support is preferred, because itserves to improve image quality. Such support can be prepared by, forexample, forming a single-layer or multi-layer film from a moltenmixture obtained by mixing a thermoplastic resin with a filler such asan inorganic pigment or a filler composed of a resin incompatible withthe thermoplastic resin, using a melt extruder, followed by stretchinguniaxially or biaxially. In this case, the void volume depends upon thekind of resin and filler selected, mixing ratio of the two, stretchingconditions, etc.

[0294] As the thermoplastic resin, a polyolefin resin such aspolypropylene and a polyethylene terephthalate resin are preferred,since they have a good crystallinity and a good stretchability, andpermit formation of the void with ease. It is preferred to use thepolyolefin resin or the polyethylene terephthalate resin as a majorcomponent and a small amount of other thermoplastic resin incombination. The inorganic pigment to be used as a filler has an averageparticle size of preferably 1 to 20 μm, and there may be used calciumcarbonate, clay, diatomaceous earth, titanium oxide, aluminum hydroxide,silica, etc. Also, as the non-compatible resin to be used as a filler,it is preferred to use polyethylene terephthalate as a filler in thecase of using polypropylene as the thermoplastic resin. Detaileddescriptions on the support having fine voids are given in JapanesePatent Application No. 290570/1999.

[0295] Additionally, the content of the filler such as an inorganicpigment in the support is generally about 2 to about 30% by volume.

[0296] The thickness of the support of the image-receiving sheet isusually 10 to 400 μm, preferably 25 to 200 μm. Also, the surface of thesupport may be subjected to a surface treatment such as corona dischargetreatment, glow discharge treatment, etc. in order to enhance adhesionto the image-receiving layer (or the cushion layer) or adhesion to theimage-forming layer of the thermal transfer sheet.

[0297] (Image-Receiving Layer)

[0298] The surface of the image-receiving sheet is preferably providedwith one or more image-receiving layers on the support in order totransfer and fix the image-forming layer. The image-receiving layer ispreferably a layer formed from an organic polymeric binder as the majorcomponent. The binder is preferably a thermoplastic resin, and examplesthereof include homopolymers and copolymers of acrylic monomers such asacrylic acid, methacrylic acid, acrylates, methacrylates, etc.;cellulose polymers such as methyl cellulose, ethyl cellulose andcellulose acetate; homopolymers and copolymers of vinyl monomers such aspolystyrene, polyvinyl pyrrolidone, polyvinyl butyral, polyvinylalcohol, polyvinyl chloride, etc.; condensation polymers such aspolyester and polyamide; and rubber polymers such as butadiene-styrenecopolymers. The binder in the image-receiving layer is preferably apolymer having a glass transition temperature (Tg) of 90° C. or less, inorder to achieve suitable adhesion to the image-forming layer. For thispurpose, a plasticizer can also be added to the image-receiving layer.Further, the binder polymer preferably has a Tg of 30° C. or more, inorder to prevent blocking among sheets. As the binder polymer in theimage-receiving layer, a polymer identical with or similar to the binderpolymer in the image-forming layer is particularly preferred, in view ofimprovement of the adhesion to the image-forming layer during laserrecording and improvement of sensitivity and image strength.

[0299] The smoothster value of the surface of the image-receiving layerat 23° C. and 55% RH is preferably 0.5 to 50 mmHg (≈0.0665 to 6.65 kPa),and Ra thereof is preferably 0.05 to 0.4 μm. Such surface is preferredin respect of transfer and image quality because it can minimizemicroscopic air gaps which prevent the image-receiving layer and theimage-forming layer from contacting with each other. The Ra value can bemeasured according to JIS B0601 using a surface roughness meter(Surfcom; made by Tokyo Seiki K.K.). The electrostatic charge potentialof the image-forming layer generated by electrostatically charging theimage-receiving sheet according to the test standard of US government4046 and earthing for one second is preferably 100 to 100 V. The surfaceresistance of the image-receiving layer at 23° C. and 55% RH ispreferably 10⁹ Ω or less. The static friction coefficient of the surfaceof the image-receiving layer is preferably 0.2 or less. The surfaceenergy of the surface of the image-receiving layer is preferably 23 to35 mJ/m².

[0300] In the case where an image is once formed on the image-receivinglayer and then re-transferred to regular printing paper or the like, atleast one of the image-receiving layers is preferably formed from aphotosetting material. Examples of compositions of such a photosettingmaterial include combinations of a) photo-polymerizable monomers thatare composed of at least one kind of multi-functional vinyl orvinylidene compound capable of forming a photo-polymerized product byaddition polymerization, b) an organic polymer, and c) aphoto-polymerization initiator, and, as needed, additives such as athermal polymerization inhibitor. As the multi-functional vinyl monomer,unsaturated esters of polyol, particularly acrylates or methacrylates(e.g., ethylene glycol diacrylate or pentaerythritol tetraacrylate) canbe used.

[0301] As the organic polymer, the above polymer for forming theimage-receiving layer can be mentioned. As the photo-polymerizationinitiator, usual radical photo-polymerization initiators such asbenzophenone, Michler's ketone and the like can be used in a proportionof 0.1 to 20% by weight of the layer.

[0302] The thickness of the image-receiving layer is 0.3 to 7 μm,preferably 0.7 to 4 μm. When the thickness is 0.3 μm or more, enoughstrength can be ensured upon re-transfer to regular printing paper. Byadjusting the thickness to be 4 μm or less, glossiness of an image afterre-transfer to regular printing paper can be depressed, thus similarityto printed products can be improved.

[0303] (Other Layers)

[0304] A cushion layer may be provided between the support and theimage-receiving layer. When the cushion layer is provided, adhesionbetween the image-forming layer and the image-receiving layer can beimproved upon laser thermal transfer, and quality of the image can beimproved. Also, even when a foreign matter is mixed in between thethermal transfer sheet and the image-receiving sheet during recording,gaps between the image-receiving layer and the image-forming layerbecome small due to deformation of the cushion layer and, as a result,the size of image defects such as missing parts can be reduced. Further,in the case where the image formed by transfer is transferred toseparately prepared regular printing paper or the like, theimage-receiving surface is deformed, depending upon the unevenness ofthe paper, and thus transferability of the image-receiving layer can beimproved and glossiness of the transferred material can be lowered,thereby improving the similarity to printed products.

[0305] The cushion layer is structured so as to be easily deformed byapplication of stress to the image-receiving layer. To achieve thiseffect, the cushion layer is preferably made of a material with a lowelasticity modulus, a material having rubber elasticity or athermoplastic resin that is easily softened by heating. The elasticitymodulus of the cushion layer is preferably 0.5 MPa to 1.0 GPa,particularly preferably 1 MPa to 0.5 GPa. at room temperature. For aforeign matter such as dust to immerse into the cushion layer, the layerhas a penetration of a loaded needle specified by JIS K2530 ofpreferably 10 or more (25° C., 100 g, 5 seconds). The glass transitiontemperature of the cushion layer is 80° C. or less, preferably 25° C. orless, and the softening point thereof is preferably 50 to 200° C. Aplasticizer can be suitably added to the binder to regulate thesephysical properties such as Tg.

[0306] Specific materials that can be used as the binder in the cushionlayer include, in addition to rubbers such as urethane rubber, butadienerubber, nitrile rubber, acrylic rubber, natural rubber, etc.,polyethylne, polypropylene, polyester, a styrene-butadiene copolymer, anethylene-vinyl acetate copolymer, an ethylene-acryl copolymer, a vinylchloride-vinyl acetate copolymer, vinylidene chloride resin,plasticizer-containing vinyl chloride resin, polyamide resin, phenolresin and the like.

[0307] Additionally, the thickness of the cushion layer varies dependingupon the resin used and upon other conditions, but is usually 3 to 100μm, preferably 10 to 52 μm.

[0308] The image-receiving layer and the cushion layer should be adheredto each other until the laser recording stage, but for transfer of theimage onto regular printing paper, these layers are preferably providedin a releasable manner. To facilitate release, a release layer of about0.1 to about 2 μm in thickness is preferably provided between thecushion layer and the image-receiving layer. In case where the thicknessof the layer is too large, it becomes difficult for the cushion layer toexhibit its performance. Thus, the thickness must be regulated dependingupon the kind of the release layer.

[0309] Specific examples of the binder for the release layer includepolyolefin, polyester, polyvinyl acetal, polyvinyl formal, polyparabanicacid, polymethyl methacrylate, polycarbonate, ethyl cellulose,nitrocellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropylcellulose, polyvinyl alcohol, polyvinyl chloride, urethane resin,fluorine-containing resin, styrenes such as polystyrene andacrylonitrile styrene, cross-linked products of these resins,thermosetting resins having a Tg of 65 C or more such as polyamide,polyimide, polyether imide, polysulfone, polyether sulfone and aramide,and cured products of these resins. As a curing agent, general curingagents such as isocyanates and melamines may be used.

[0310] In selecting the binder for the release layer in consideration ofthe above physical properties, polycarbonate, acetal and ethyl celluloseare preferred in the point of storage properties and, further, it isparticularly preferred to use the acrylic resin in the image-receivinglayer because a good releasing properties are obtained upon re-transferof an image having been thermally transferred by the laser recording.

[0311] Also, it is possible to separately use, as a release layer, alayer undergoing an extreme reduction of adhesion to the imabe-receivinglayer upon cooling. Specifically, such layer contains a heat-meltablecompound such as a wax or a binder, or a thermoplastic resin as a majorcomponent.

[0312] As the heat-meltable compound, there are illustrated those whichare described in Japanese Patent Laid-Open No. 193886/1988.Microcrystalline wax, paraffin wax and carnauba wax are particularlypreferably used. As the thermoplastic resin, ethylenic copolymers suchas an ethylene-vinyl acetate-based resin, cellulose-based resin, etc.are preferably used.

[0313] To such release layer may be added, as additives, a higher fattyacid, a higher alcohol, a higher fatty acid ester, an amide, a higheramine, etc., as needed.

[0314] Another structure of the release layer is such that it undergoesmelting or softening upon heating to cause cohesive failure itself, thusshowing releasing properties. It is preferred to incorporate asuper-cooling material in such release layer.

[0315] Examples of the super-cooling material includepoly-ε-caprolactone, polyoxyethylene, benzotriazole, tribenzylamine,vaniline, etc.

[0316] In a release layer of a further structure is contained a compoundcapable of reducing adhesion to the image-receiving layer. Examples ofsuch compound include silicone-based resin such as silicone oil; Teflon;fluorine-containing resins such as fluorine-containing acrylic resin;polysiloxane resins; acetal-based resins such as polyvinyl butyral,polyvinyl acetal and polyvinyl formal; solid waxes such as polyethylenewax and amide wax; and surfactants such as fluorine-containingsurfactants and phosphate-based surfactants.

[0317] As a method for forming the release layer, there may be applied acoating method of dissolving, or dispersing in a latex form, thematerial in a solvent using a blade coater, a roll coater, a bar coater,a curtain coater or a gravure coater and coating the resultant solutionor dispersion, and a laminating method by hot-melt extrusion. Therelease layer can be formed on the cushion layer by coating. Or, thereis a method of forming the release layer by coating the solution or thelatex dispersion in a solvent on a tentative base, and laminating thethus formed layer on the cushion layer, followed by delaminating thetentative base.

[0318] The image-receiving sheet to be combined with the thermaltransfer sheet may have a structure wherein the image-receiving layeralso functions as the cushion layer. In this case, the image-receivingsheet may have a structure of support/cushioning image-receiving layeror a structure of support/undercoating layer/cushioning image-receivinglayer. In this case, too, it is preferred to provide the cushioningimage-receiving layer in a releasable manner so as to enable tore-transfer to regular printing paper. In this case, the imagere-transferred to regular printing paper becomes an image excellent inglossiness.

[0319] Additionally, the thickness of the cushioning image-receivinglayer is 5 to 100 μm, preferably 10 to 40 μm.

[0320] A backing layer provided in the image-receiving sheet on theopposite side of the support to the side on which the image-receivinglayer is provided serves to improve conveying performance, thus beingpreferred. Addition of a surfactant, an antistatic agent formed by tinoxide fine particles, or a matting agent formed by silicon oxide or PMMAparticles is preferred in the point of improving conveying performancewithin the recording apparatus.

[0321] The additives can be added not only to the backing layer but alsoto the image-receiving layer and other layers, if necessary. Kinds ofthe additives are not generally described depending upon the end-usebut, with the matting agent, particles of 0.5 to 10 μm in averageparticle size can be added to the layer in a content of about 0.5 toabout 80%. The antistatic agent can be appropriately selected and usedfrom various surfactants and electricaly conductive agents such that thesurface resistance of the backing layer is preferably 10¹² Ω or less,more preferably 10⁹ Ω or less under the conditions of 23° C. and 50% RH.

[0322] As the binder to be used in the backing layer, there may be usedgeneral-purpose polymers such as gelatin, polyvinyl alcohol, methylcellulose, nitrocellulose, acetyl cellulose, aromatic polyamide resin,silicone resin, epoxy resin, alkyd resin, phenol resin, melamine resin,fluorine-containing resin, polyimide resin, urethane resin, acrylicresin, urethane-modified silicone resin, polyethylene resin,polypropylene resin, polyester resin, Teflon resin, polyvinyl butyralresin, vinyl chloride-based resin, polyvinyl acetate, polycarbonate,organo-boron compound, aromatic esters, fluorinated polyurethane,polyether sulfone, etc.

[0323] It is effective for preventing removal of the matting agent orimproving flaw resistance of the backing layer to use a cross-linkablewater-soluble binder as the binder for the backing layer andcross-linking it. Also, it is greatly effective for preventing blockingduring storage.

[0324] As this cross-linking means, one of, or a combination of, heat,actinic rays and pressure may be employed with no limitation dependingupon the properties of the cross-linking agent to be used. In somecases, any adhesive layer may be provided on the opposite side of thesupport to the side on which the backing layer is provided, for thepurpose of imparting adhesion properties to the support.

[0325] As the matting agent to be preferably added to the backing layer,organic or inorganic fine particles may be used. Examples of the organicmatting agent include fine particles of radical polymerization typepolymers such as polymethyl methacrylate (PMMA), polystyrene,polyethylene, polypropylene and the like, and fine polymers ofcondensation type polymers such as polyester, polycarbonate and thelike.

[0326] The backing layer is preferably provided in an amount of about0.5 to about 5 g/m². In case when the amount is less than 0.5 g/m²,there results unstable coating properties, and the problem of removal ofthe matting agent is liable to arise. Also, in case when coated in anamount much larger than 5 g/m², particle size of a preferred mattingagent becomes so large that embossing of the image-receiving layersurface by the backing layer takes place during storage, which is liableto cause missing or unevenness of a recorded image particularly withthermal transfer of transferring a thin image-forming layer.

[0327] The matting agent preferably has a number average particle sizegreater than the thickness of the binder alone of the backing layer by2.5 to 20 μm. Among the matting agents, those which contain particles of8 μm or more in size in a content of 5 mg/m² or more, preferably 6 to600 mg/m², are necessary. Such matting agents serve to prevent foreignmatter troubles. Also, use of a matting agent having such a narrowparticle size distribution that a σ/rn value (=coefficient of variation)obtained by dividing the standard deviation of the particle sizedistribution by the number average particle size becomes 0.3 or lessserves to remove defects to be otherwise generated due to particleshaving an abnormally large particle size and to provide desiredperformance even when added in a smaller amount. This coefficient ofvariation is more preferably 0.15 or less.

[0328] To the backing layer is preferably added an antistatic agent forthe purpose of preventing adhesion of a foreign matter due to frictionalcharging with conveying rolls. As the antistatic agent, there may bewidely used cationic surfactants, anionic surfactants, nonionicsurfactants, high molecular antistatic agents, electroconductive fineparticles as well as those compounds described in “11290 No KagakuShohin” published by Kagaku Kogyo Nippo Sha, pp.875 to 876.

[0329] As the antistatic agent to be used in the backing layer, carbonblack, a metal oxide such as zinc oxide, titanium oxide or tin oxide,and conductive fine particles such as an organic semiconductor arepreferably used among the above-described materials. Particularly, useof conductive fine particles is preferred because the antistatic agentis not released from the backing layer, and a stable antistatic effectis obtained regardless of environment.

[0330] Also, various active agents, silicone oil, and a parting agentsuch as a fluorine-containing resin may be added to the backing layerfor the purpose of imparting coating properties or parting properties.

[0331] The backing layer is particularly preferred when the softeningpoints of the cushion layer and the image-receiving layer measuredaccording to TMA (Thermomechanical Analysis) are 70° C. or less.

[0332] The TMA softening point is determined by raising the temperatureof a sample to be measured at a constant rate while applying a constantload, and observing the phase of the sample. In the invention, atemperature at which phase of the sample start to change is determinedto be the TMA softening point. Measurement of the softening point by TMAcan be conducted using an apparatus such as Thermoflex made by RigakuDenki Sha.

[0333] The thermal transfer sheet and the image-receiving sheet can beused as a laminate wherein the image-forming layer of the thermaltransfer sheet is superimposed on the image-receiving layer of theimage-receiving sheet, for forming an image.

[0334] The laminate consisting of the thermal transfer sheet and theimage-receiving sheet can be formed by various methods. For example, thelaminate can be easily obtained by super imposing the image-forminglayer of the thermal transfer sheet on the image-receiving layer of theimage-receiving sheet, and passing the resulting laminate betweenpressing and heating rollers. A heating temperature in this case ispreferably 160° C. or less, more preferably 130° C. or less.

[0335] As another method of obtaining the laminate, a vacuum adhesionmethod can also be preferably used. The vacuum adhesion method is amethod in which the image-receiving sheet is first wound on a drumhaving vacuum-drawing suction holes and then the thermal transfer sheetslightly larger than the image-receiving sheet is vacuum-bonded to theimage-receiving sheet under uniform extrusion of air by squeeze rollers.As another method, there is also a method in which the image-receivingsheet is stretched and mechanically stuck to a metal drum, and then thethermal transfer sheet is mechanically stretched and stuck to theimage-receiving sheet in the same manner. Among these methods, thevacuum adhesion method is particularly preferable in view of rapid andeasy uniform lamination without requiring regulation of the temperatureof heat rollers or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0336]FIG. 1 is a drawing showing the outline of the mechanism offorming a multi-color image by thin-film thermal transfer using a laserlight.

[0337]FIG. 2 is a drawing showing an example of a constitution of arecording apparatus for laser thermal transfer.

[0338]FIG. 3 is a drawing showing an example of a constitution of athermal transfer apparatus.

[0339]FIG. 4 is a drawing showing an example of a constitution of asystem using a recording apparatus, FINALPROOF, for laser thermaltransfer.

[0340]FIG. 5 shows the results of Examples and Comparative Examples onan a*b* plane of an L*a*b* calorimetric system.

DESCRIPTION OF THE REFERENCE NUMERALS AND SIGNS

[0341]1 recording apparatus; 2 recording head; 3 sub-scanning rail; 4recording drum; 5 thermal transfer sheet-loading unit; 6 imag-receivingsheet roll; 7 conveying rollers; 8 squeeze rollers; 9 cutter; 10 thermaltransfer sheet; 10K, 10C, 10M, 10Y, 10R thermal transfer sheet rolls; 12support; 13 light-to-heat conversion layer; 16 image-forming layer; 20image-receiving sheet; 22 support for the image-receiving sheet; 24image-receiving layer; 30 laminate; 31 discharge support; 32 wasteoutlet; 33 discharge outlet; 34 air; 35 waste box; 42 regular paper; 43heat roller; 44 inserting support; 45 mark showing the placing position;46 inserting rollers; 47 guide made of a heat-resistant sheet; 48peeling claw; 49 guide plate; 50 discharge outlet

BEST MODE FOR CARRYING OUT THE INVENTION

[0342] Hereinafter, Examples of the invention are described, whichhowever do not limit the invention. Additionally, unless otherwisespecified, “parts” means “parts by weight”.

EXAMPLE 1

[0343] Preparation of Thermal Transfer Sheet R (Red)

[0344] [Formation of a Backing Layer]

[0345] [Preparation of a Coating Solution for a First Backing Layer]Aqueous dispersion of acrylic resin   2 parts (Julimer ET410; solidcontent: 20% by weight; made by Nippon Junyaku K.K.) Antistatic agent(aqueous dispersion of 7.0 parts tin oxide-antimony oxide) (averageparticle size: 0.1 μm; 17% by weight) Polyoxyethylene phenyl ether 0.1part Melamine compound 0.3 part (Sumitics Resin M-3; made by SumitomoChemical Industries Co., Ltd.) Distilled water to make 100 parts

[0346] [Formation of the First Backing Layer]

[0347] One side (back side) of a 75-μm thick biaxially stretchedpolyethylene terephthalate support (Ra of both sides: 0.01 μm) wassubjected to corona discharge treatment, and the coating solution forthe first backing layer was coated thereon in a dry thickness of 0.03μm, followed by drying at 180° C. for 30 seconds to form the firstbacking layer. The Young's modulus of the support in the longitudinaldirection was 450 Kg/mm2 (≈4.4 GPa), and the Young's modulus in thetransverse direction was 500 Kg/mm² (≈4.9 GPa). The F-5 value of thesupport in the longitudinal direction was 10 Kg/mm² (≈9.8 MPa), and theF-5 value in the transverse direction was 13 Kg/mm² (≈127.4 MPa). Theheat-shrinking ratio of the support at 100° C. for 30 minutes in thelongitudinal direction was 0.3%, and that in the transverse directionwas 0.1%. The breaking strength in the longitudinal direction was 20Kg/mm² (≈0.196 MPa), and that in the transverse direction was 25 Kg/mm²(≈245 MPa). The elasticity modulus was 400 Kg/mm² (≈3.9 GPa).

[0348] [Preparation of a Coating Solution for a Second Backing Layer]Polyolefin (chemipearl S-120; 27% 3.0 parts by weight; made by MitsuiSekiyu Kagaku K.K.) Antistatic agent (aqueous dispersion of 2.0 partstin oxide-antimony oxide) (average particle size: 0.1 μm; 17% by weight)Colloidal silica (Snowtex C; 20% by weight; 2.0 parts made by NissanKagaku K.K.) Epoxy compound (Dinacol EX-614B; made by 0.3 part NagaseKasei K.K.) Distilled water to make 100 parts

[0349] [Formation of the Second Backing Layer]

[0350] On the first backing layer was coated the coating solution forthe second backing layer in a dry thickness of 0.03 μm, followed bydrying at 170° C. for 30 seconds to form the second backing layer.

[0351] [Formation of a Light-to-Heat Conversion Layer]

[0352] [Preparation of a Coating Solution for the Light-to-HeatConversion Layer]

[0353] The following ingredients were mixed under stirring with astirrer to prepare a coating solution for the light-to-heat conversionlayer.

[0354] [Composition of the Coating Solution for the Light-to-HeatConversion Layer]

[0355] Infrared absorbing colorant (NK-2014; 7.6 parts made by NihonKanko Shikiso Co., Ltd.;

[0356] cyanine colorant of the following structure:

[0357] wherein R represents CH₃, and X⁻ represents ClO₄ ⁻. Polyimideresin of the following structure: 29.3 parts (“Rikacoat SN-20F; made byNew Japan Chemical Co., Ltd.; thermal decomposition temperature: 510°C.)

[0358] wherein R₁ represents SO₂, and R₂ represents

or

Exon naphtha 5.8 parts N-methylpyrrolidone (NMP) 1500 parts Methyl ethylketone 360 parts Surfactant (Megafac F-176PF; made by Dai-nippon Ink &Chemicals, Inc.; 0.5 part F-series surfactant) Dispersion of a mattingagent of the following composition: 14.1 parts

[0359] Preparation of the Dispersion of the Matting Agent:

[0360] 10 parts of truly spherical silica fine particles of 1.5 μm inaverage particle size (Seahoster KEP 150 made by Nihon Shokubai K.K.), 2parts of a dispersant polymer (acrylate-styrene copolymer; made byJohnson Polymer K.K.; Juncryl 611), 16 parts of methyl ethyl ketone and64 parts of N-methylpyrrolidone were mixed, and the resulting mixtureand 30 parts of glass beads of 2 mm in diameter were placed in a 200-mlpolyethylene vessel, followed by dispersing in a paint shaker (made byToyo Seiki) for 2 hours to obtain a dispersion of silica fine particles.

[0361] [Formation of a Light-to-Heat Conversion Layer on the Surface ofthe Support]

[0362] On the one surface of the 75-μm thick polyethylene terephthalatefilm (support) was coated the above-described coating solution for thelight-to-heat conversion layer using a wire bar, followed by drying thecoated product in a 120° C. oven for 2 minutes to form the light-to-heatconversion layer on the support. The optical density of the thusobtained light-to-heat conversion layer at a wavelength of 808 nm wasmeasured to be OD=0.93 using a UV-spectrophotometer, UV-240, made byShimazu Seisakusho. The thickness was measured to be 0.3 μm on theaverage by observing cross section of the light-to-heat conversion layerusing a scanning type electron microscope.

[0363] [Formation of an Image-Forming Layer]

[0364] [Preparation of a Coating Solution for a Red Image-Forming Layer]

[0365] The following ingredients were placed in a mill of a kneader, anda shearing force was applied thereto while adding thereto a solvent byportions to conduct treatment before dispersing. To the resultingdispersion was further added a solvent to adjust so as to finally obtainthe following formulation, followed by conducting sand mill dispersionfor 2 hours to obtain a pigment dispersion mother liquor.

[0366] [Formulation of the Red Pigment Dispersion Mother Liquor] Pigmentdispersion 1 Pigment Red 48:1 (C.I. No. 15865:1)  8.93 parts (Lionol Red2B-FG3300; made by Toyo Ink Mfg. Co., Ltd.) Polyvinyl butyral (Esreck BBL-SH;  7.50 parts made by Sekisui Chemical Co., Ltd.) Dispersing aid(Solsperse S-20000;  0.47 part made by ICI) n-propyl alcohol 83.10 partsPigment dispersion 2 Pigment Red 48:3 (C.I. No. 15865:3)  8.93 parts(Symuler Red 3108; made by Dai-nippon Ink & Chemicals, Inc.) Polyvinylbutyral (Esreck B BL-SH;  7.50 parts made by Sekisui Chemical Co., Ltd.)Dispersing aid (Solsperse S-20000;  0.47 part made by ICI) n-propylalcohol 83.10 parts

[0367] Particles of the thus obtained pigment dispersions 1 and 2 weremeasured using a laser-scattering type particle sizedistribution-measuring meter, and it was found that the average particlesizes thereof were 192 nm and 193 nm, respectively.

[0368] Next, the following ingredients were mixed under stirring with astirrer to prepare a coating solution for a red image-forming layer.

[0369] [Formulation of a Coating Solution for the Red Image-FormingLayer] n-propyl alcohol 321.5 parts Methyl ethyl ketone  89.3 parts Waxcompounds (Stearic amide “Newtron 2”; made by 0.824 part Nippon FineChemical Co., Ltd.) (Behenic amide “Diamid BM”; made by 0.824 partNippon Kasei Chemical Co., Ltd.) (Lauric amide “Diamid Y”; made by 0.824part Nippon Kasei Chemical Co., Ltd.) (Palmitic amide “Diamid KP”; madeby 0.824 part Nippon Kasei Chemical Co., Ltd.) (Oleic amide “DiamidO-200”; made by 0.824 part Nippon Kasei Chemical Co., Ltd.) (Erucicamide “Diamid L-200”; made by 0.824 part Nippon Kasei Chemical Co.,Ltd.) Rosin 2.360 parts (KE-311; made by Arakawa Kagaku Co., Ltd.; resiningredients: abietic acid 30 to 40%; neoabietic acid 10 to 20%;dihydroabietic acid 14%; tetrahydroabietic acid 14%) Polyvinyl butyral(Esreck B BL-SH; 1.455 parts made by Sekisui Chemical Co., Ltd.) Pigmentdispersion 1 77.40 parts Pigment dispersion 2 24.40 parts Surfactant(Megafac F-176PF; solid 1.216 parts content: 20%; made by Dai-nippon Ink& Chemicals, Inc.)

[0370] [Formation of the Red Image-Forming Layer on the Surface of theLight-to-Heat Conversion Layer]

[0371] On the surface of the light-to-heat conversion layer was coatedthe above-mentioned coating solution for the red image-forming layerusing a wire bar for one minute, followed by drying the coated productin a 100° C. oven for 2 minutes to form the red image-forming layer onthe light-to-heat conversion layer. Thus, the thermal transfer sheet Rwas prepared by these steps, wherein the light-to-heat conversion layerand the red image-forming layer were provided in this order on thesupport.

[0372] The thickness of the red image-forming layer of the thermaltransfer sheet R was measured to be 0.71 μm on the average.

[0373] Physical properties of the thus obtained image-forming layer wereas follows.

[0374] The surface hardness of the image-forming layer is preferably 10g or more when measured using a sapphire needle, and was specifically200 g or more.

[0375] The smoothster value of the surface is preferably 0.5 to 50 mmHg(≈0.0665 to 6.65 kPa) at 23° C. and 55% RH, and was specifically 27 mmHg(≈3.60 kPa).

[0376] The static friction coefficient of the surface is preferably 0.2or less, and was specifically 0.08.

[0377] The contact angle with water was 46.8 degrees.

[0378] Preparation of Thermal Transfer Sheet Y

[0379] A thermal transfer sheet Y was prepared in the same manner aswith the preparation of the thermal transfer sheet R except for using acoating solution for a yellow image-forming layer of the followingformulation in place of the coating solution for the red image-forminglayer. The thickness of the image-forming layer of the resulting thermaltransfer sheet Y was 0.42 μm.

[0380] [Formulation of the Yellow Pigment Dispersion Mother Liquor]Formulation 1 of yellow pigment dispersion mother liquor Polyvinylbutyral (Esreck B BL-SH;  7.1 parts made by Sekisui Chemical Co., Ltd.)Pigment Yellow 180 (C.I. No. 21290) 12.9 parts (Novoperm Yellow P-HG;made by Clariant Japan K.K.) Dispersing aid (Solsperse S-20000;  0.6part made by ICI) n-Propyl alcohol 79.4 parts

[0381] [Formulation of the Yellow Pigment Dispersion Mother Liquor]Formulation 2 of yellow pigment dispersion mother liquor Polyvinylbutyral (Esreck B BL-SH;  7.1 parts made by Sekisui Chemical Co., Ltd.)Pigment Yellow 139 (C.I. No. 56298) 12.9 parts (Novoperm Yellow M2R 70;made by Clariant Japan K. K.) Dispersing aid (Solsperse S-20000;  0.6part made by ICI) n-Propyl alcohol 79.4 parts

[0382] [Formulation of a Coating Solution for the Red Image-FormingLayer] The above-mentioned yellow pigment  126 parts dispersion motherliquors (Formulation 1 of the yellow pigment:Formulation 2 of theyellowigment 2 = 95:5) Polyvinyl butyral (Esreck B bBL-SH;  4.6 partsmade by Sekisui Chemical Co., Ltd.) Wax compounds (Stearic amide“Newtron 2”; made by  0.7 part Nippon Fine Chemical Co., Ltd.) (Behenicamide “Diamid BM”; made by  0.7 part Nippon Kasei Chemical Co., Ltd.)(Lauric amide “Diamid Y”; made by  0.7 part Nippon Kasei Chemical Co.,Ltd.) (Palmitic amide “Diamid KP”; made by  0.7 part Nippon KaseiChemical Co., Ltd.) (Erucic amide “Diamid L-200”; made by  0.7 partNippon Kasei Chemical Co., Ltd.) (Oleic amide “Diamid O-200”; made by 0.7 part Nippon Kasei Chemical Co., Ltd.) Nonionic surfactant(Chemistat 1100;  0.4 part made by Sanyo Chemical Industries, Ltd.)Rosin 2.4 parts (KE-311; made by Arakawa Kagaku Co., Ltd.) Surfactant(Megafac F-176PF; solid  0.8 part content: 20%; made by Dai-nippon Ink &Chemicals, Inc.) n-Propyl alcohol  793 parts Methyl ethyl ketone  198parts

[0383] Physical properties of the thus obtained image-forming layer wereas follows.

[0384] The surface hardness of the image-forming layer is preferably 10g or more when measured using a sapphire needle, and was specifically200 g or more.

[0385] The smoothster value of the surface is preferably 0.5 to 50 mmHg(≈0.0665 to 6.65 kPa) at 23° C. and 55% RH, and was specifically 2.3mmHg (≈0.31 kPa).

[0386] The static friction coefficient of the surface is preferably 0.2or less, and was specifically 0.1.

[0387] The surface energy was 24 mJ/m². The contact angle with water was108.1 degrees. The deformation ratio of the light-to-heat conversionlayer upon recording with a laser light of 100 W/mm² or more in lightintensity on their radiated surface at a line speed of 1 m/sec or morewas 150%.

[0388] Preparation of Thermal Transfer Sheet M

[0389] A thermal transfer sheet M was prepared in the same manner aswith the preparation of the thermal transfer sheet R except for using acoating solution for a magenta image-forming layer of the followingformulation in place of the coating solution for the red image-forminglayer. The thickness of the image-forming layer of the resulting thermaltransfer sheet M was 0.38 μm.

[0390] [Formulation of the Magenta Pigment Dispersion Mother Liquor]Formulation 1 of magenta pigment dispersion mother liquor Polyvinylbutyral (Denka 12.6 parts Butyral #2000-L; made by Denki Kagaku KoogyoK.K.; Vicat softening point: 57 ° C.) Pigment Red 57:1 (C.I. No. 15850)15.0 parts (Symuler Brilliant Carmine 6B-229; made by Dai-nippon Ink &Chemicals, Inc.) Dispersing aid (Solsperse S-20000;  0.6 part made byICI) n-Propyl alcohol 80.4 parts

[0391] [Formulation of the Magenta Pigment Dispersion Mother Liquor]Formulation 2 of magenta pigment dispersion mother liquor Polyvinylbutyral (Denka 12.6 parts Butyral #2000-L; made by Denki Kagaku KogyoK.K.; Vicat softening point: 57° C.) Pigment Red 57:1 (C.I. No. 15850:1)15.0 parts (Lionol Red 6B-4290G; made by Toyo Ink Mfg. Co., Ltd.)Dispersing aid (Solsperse S-20000;  0.6 part made by ICI) n-Propylalcohol 79.4 parts

[0392] [Formulation of a Coating Solution for the Magenta Image-FormingLayer] The above-mentioned magenta pigment 163 parts dispersion motherliquors (Formulation 1 of the yellow pigment: Formulation 2 of theyellow pigment 2 = 95:5(parts)) Polyvinyl butyral (Denka Butyral  4.0parts #2000-L; made by Denki Kagaku Kogyo K.K.; Vicat softening point:57° C.) Wax compounds (Stearic amide “Newtron 2”; made by  1.0 partNippon Fine Chemical Co., Ltd.) (Behenic amide “Diamid BM”; made by  2.0part Nippon Kasei Chemical Co., Ltd.) (Palmitic amide “Diamid KP”; madeby  1.0 part Nippon Kasei Chemical Co., Ltd.) (Erucic amide “DiamidL-200”; made by  1.0 part Nippon Kasei Chemical Co., Ltd.) (Oleic amide“Diamid O-200”; made by  1.0 part Nippon Kasei Chemical Co., Ltd.)Nonionic surfactant (Chemistat 1100;  0.7 part made by Sanyo ChemicalIndustries, Ltd.) Rosin  4.6 parts (KE-311; made by Arakawa Kagaku Co.,Ltd.) Pentaerythritol tetraacrylate (NK  2.5 parts ester A-TMMT; made byShin-Nakamura Kagaku K.K.) Surfactant (Megafac F-176PF; solid  1.3 partcontent: 20%; made by Dai-nippon Ink & Chemicals, Inc.) n-Propyl alcohol848 parts Methyl ethyl ketone 246 parts

[0393] Physical properties of the thus obtained image-forming layer wereas follows.

[0394] The surface hardness of the image-forming layer is preferably 10g or more when measured using a sapphire needle, and was specifically200 g or more.

[0395] The smoothster value of the surface is preferably 0.5 to 50 mmHg(≈0.0665 to 6.65 kPa) at 23° C. and 55% RH, and was specifically 3.5mmHg (≈0.47 kPa).

[0396] The static friction coefficient of the surface is preferably 0.2or less, and was specifically 0.08.

[0397] The surface energy was 25 mJ/m². The contact angle with water was98.8 degrees. The deformation ratio of the light-to-heat conversionlayer upon recording with a laser light of 1000 W/mm² or more in lightintensity on the irradiated surface at a line speed of 1 m/sec or morewas 160%.

[0398] Preparation of Thermal Transfer Sheet C

[0399] A thermal transfer sheet C was prepared in the same manner aswith the preparation of the thermal transfer sheet R except for using acoating solution for a cyan image-forming layer of the followingformulation in place of the coating solution for the red image-forminglayer. The thickness of the image-forming layer of the resulting thermaltransfer sheet C was 0.45 μm.

[0400] [Formulation of the Magenta Pigment Dispersion Mother Liquor]Formulation 1 of magenta pigment dispersion mother liquor: Polyvinylbutyral (Esreck B BL-SH; 12.6 parts made by Sekisui Chemical Co., Ltd.)Pigment Blue 15:4 (C.I. No. 74160) 15.0 parts (Cyanine Blue 700-10FG;made by Toyo Ink Mfg. Co., Ltd.) Dispersing aid (PW-36; made by  0.6part Kusumoto Kasei K.K.) n-Propyl alcohol  110 parts

[0401] [Formulation of the Cyan Pigment Dispersion Mother Liquor]Formulation 2 of cyan pigment dispersion mother liquor: Polyvinylbutyral (Esreck B BL-SH; 12.6 parts made by Sekisui Chemical Co., Ltd.)Pigment Blue 15 (C.I. No. 74160) 15.0 parts (Lionol Blue 7027; made byToyo Ink Mfg. Co., Ltd.) Dispersing aid (PW-36; made by  0.6 partKusumoto Kasei K.K.) n-Propyl alcohol  110 parts

[0402] [Formulation of a Coating Solution for the Cyan Image-FormingLayer] The above-mentioned cyan pigment 118 parts dispersion motherliquors (Formulation 1 of the cyan pigment: Formulation 2 of the cyanpigment 2 = 90:10 (parts)) Polyvinyl butyral (Esreck B BL-SH;  4.0 partsmade by Sekisui Chemical Co., Ltd.) Inorganic pigment “MEK-ST”  1.3parts Wax compounds (Stearic amide “Newtron 2”; made by  1.0 part NipponFine Chemical Co., Ltd.) (Behenic amide “Diamid EM”; made by  1.0 partNippon Kasei Chemical Co., Ltd.) (Lauric amide “Diamid Y”; made by  1.0part Nippon Kasei Chemical Co., Ltd.) (Palmitic amide “Diamid KP”; madeby  1.0 part Nippon Kasei Chemical Co., Ltd.) (Erucic amide “DiamidL-200”; made by  1.0 part Nippon Kasei Chemical Co., Ltd.) (Oleic amide“Diamid O-200”; made by  1.0 part Nippon Kasei Chemical Co., Ltd.) Rosin 2.8 parts (KE-311; made by Arakawa Kagaku Co., Ltd.) Pentaerythritoltetraacrylate (NK  1.7 parts ester A-TMMT; made by Shin-Nakamura KagakuK.K.) Surfactant (Megafac F-176PF; solid  1.7 part content: 20%; made byDai-nippon Ink & Chemicals, Inc.) n-Propyl alcohol 890 parts Methylethyl ketone 247 parts

[0403] Physical properties of the thus obtained image-forming layer wereas follows.

[0404] The surface hardness of the image-forming layer is preferably 10g or more when measured using a sapphire needle, and was specifically200 g or more.

[0405] The smoothster value of the surface is preferably 0.5 to 50 mmHg(≈0.0665 to 6.65 kPa) at 23° C. and 55% RH, and was specifically 7.0mmHg (≈0.93 kPa).

[0406] The static friction coefficient of the surface is preferably 0.2or less, and was specifically 0.08.

[0407] The surface energy was 25 mJ/m2. The contact angle with water was98.8 degrees. The deformation ratio of the light-to-heat conversionlayer upon recording with a laser light of 1000 W/mm² or more in lightintensity on the irradiated surface at a line speed of 1 m/sec or morewas 165%.

[0408] Preparation of an Image-Receiving Sheet

[0409] A coating solution of the following formulation for a cushionlayer and a coating solution of the following formulation for animage-receiving layer were prepared. 1) Coating solution for a cushionlayer Vinyl chloride-vinyl acetate copolymer  20 parts (main binder;MPR-TSL; made by Nisshin Chemical Industry Co., Ltd.) Plasticizer(Paraplex G-40; made by  10 parts CP. HALL. COMPANY) Surfactant(fluorine-containing type; 0.5 part coating aid; Megafac F-177; made byDai-nippon Ink & Chemicvals, Inc.) Antistatic agent (quaternary ammonium0.3 part salt; SAT-5 Supper (IC); made by Nippon Junyaku Co., Ltd.)Methyl ethyl ketone  60 parts Toluene 10 parts N,N-Dimethylformamide   3parts 2) Coating solution for an image-receiving layer Polyvinyl butyral(Esreck B BL-SH; 8.0 parts made by Sekisui Chemical Co., Ltd.)Antistatic agent (Sunstat 2012A; made 0.7 part by Sanyo ChemicalIndustries, Ltd.) Surfactant (Megafac F-176PF; solid 0.1 part content:20%; made by Dai-nippon Ink & Chemicals, Inc.) n-Propyl alcohol  20parts Methanol  20 parts 1-Methoxy-2-propanol  50 parts

[0410] Using a small-width coating machine, the above coating solutionfor the cushion layer was coated onto a white PET support (Lumilar#130E58; made by Toray Co., Ltd.; thickness: 130 μm), followed by dryingthe coated layer. Then, the coating solution for the image-receivinglayer was coated thereon and dried. The amounts of the coating solutionswere regulated such that the thickness of the cushion layer after dryingwas about 20 μm, and the thickness of the image-receiving layer wasabout 2 μm. The white PET support is a void-containing plastic supportcomposed of a laminate (total thickness: 130 μm; specific gravity: 0.8)of a void-containing polyethylene terephthalate layer (thickness: 116μm; void volume: 20%) and a titanium oxide-containing polyethyleneterephthalate layer (thickness: 7 μm; content of titanium oxide: 2%)provided on both sides thereof. The prepared material was wound into aroll, stored at room temperature for one week and used for imagerecording with a laser light as described below.

[0411] Physical properties of the thus obtained image-receiving layerwere as follows.

[0412] The surface roughness Ra is preferably 0.4 to 0.01 μm, and wasspecifically 0.02 μm.

[0413] The surface waviness of the image-receiving layer is preferably 2μm or less, and was specifically 1.2 μm.

[0414] The smoothster value of the surface of the image-receiving layeris preferably 0.5 to 50 mmHg (≈0.0665 to 6.65 kPa) at 23° C. and 55% RH,and was specifically 0.8 mmHg (=. 0.11 kPa).

[0415] The static friction coefficient of the surface of theimage-receiving layer is preferably 0.8 or less, and was specifically0.37.

[0416] The surface energy of the surface of the image-receiving layerwas 29 mJ/m². The contact angle with water was 85 degrees.

[0417] Thus, there was obtained a multi-color image-forming materialcomposed of the thermal transfer sheets R, Y, M and C, and theimage-receiving sheet.

EXAMPLE 2

[0418] Preparation of Thermal Transfer Sheet B (Blue)

[0419] A thermal transfer sheet B was prepared in the same manner aswith the preparation of the thermal transfer sheet R except for using acoating solution for a blue image-forming layer of the followingformulation in place of the coating solution for the red image-forminglayer. The thickness of the image-forming layer of the resulting thermaltransfer sheet B was 0.95 μm.

[0420] [Formulation of the Blue Pigment Dispersion Mother Liquor]

[0421] Pigment Dispersion 3 Pigment Blue 60 (C.I. No. 69800)  4.02 parts(Fastogen Super Blue 6070S; made by Dai-nippon Ink & Chemicals, Inc.)Pigment Blue 15:6 (C.I. No. 74160)  4.02 parts (Lionol Blue 7600; madeby Toyo Ink Mfg. Co., Ltd.) Pigment Violet 23 (C.I. No. 51319)  0.89part (Hosterperm Violet RL-NF; made by Clariant Japan K.K.) Polyvinylbutyral (Esreck B BL-SH;  7.50 parts made by Sekisui Chemical Co., Ltd.)Dispersing aid (Solsperse S-20000;  0.47 part made by ICI) n-Propylalcohol 83.10 parts

[0422] Particle size of the thus obtained pigment dispersion wasmeasured using a laser-scattering type particle sizedistribution-measuring meter, which indicated that the average particlesize was 242 nm.

[0423] Next, the following ingredients were mixed under stirring toprepare a coating solution for a blue image-forming layer.

[0424] [Formulation of a Coating Solution for the Blue Image-FormingLayer] n-Propyl alcohol  321.5 parts Methyl ethyl ketone  89.3 parts Waxcompounds (Stearic amide “Newtron 2”; made by  0.824 part Nippon FineChemical Co., Ltd.) (Behenic amide “Diamid BM”; made by  0.824 partNippon Kasei Chemical Co., Ltd.) (Lauric amide “Diamid Y”; made by 0.824 part Nippon Kasei Chemical Co., Ltd.) (Palmitic amide “DiamidKP”; made by  0.824 part Nippon Kasei Chemical Co., Ltd.) (Oleic amide“Diamid O-200”; made by  0.824 part Nippon Kasei Chemical Co., Ltd.)(Erucic amide “Diamid L-200”; made by  0.824 part Nippon Kasei ChemicalCo., Ltd.) Rosin  2.360 parts (KE-311; made by Arakawa Kagaku Co., Ltd.)Polyvinyl butyral (Esreck B BL-SH;  1.455 parts made by Sekisui ChemicalCo., Ltd.) Pigment dispersion 3 101.80 parts Surfactant (MegafacF-176PF; solid  1.216 part content: 20%; made by Dai-nippon Ink &Chemicals, Inc.)

[0425] Thermal transfer sheet Y, thermal transfer sheet M, thermaltransfer sheet C, thermal transfer sheet K, and an image-forming sheetare the same as in Example 1.

[0426] Thus, there was obtained a multi-color image-forming materialcomposed of the thermal transfer sheets B, Y, M and C, and theimage-receiving sheet.

EXAMPLE 3

[0427] Preparation of Thermal Transfer Sheet G (Green)

[0428] A thermal transfer sheet G was prepared in the same manner aswith the preparation of the thermal transfer sheet R except for using acoating solution for a green image-forming layer of the followingformulation in place of the coating solution for the red image-forminglayer. The thickness of the image-forming layer of the resulting thermaltransfer sheet G was 0.70 μm.

[0429] [Formulation of the Green Pigment Dispersion Mother Liquor]Pigment dispersion 4 Pigment Green 7 (C.I. No. 74260)  8.93 parts(Fastogen Green S; made by Dai-nippon Ink & Chemicals, Inc.) Polyvinylbutyral (Esreck B BL-SH;  7.50 parts made by Sekisui Chemical Co., Ltd.)Dispersing aid (Solsperse S-20000;  0.47 part made by ICI) n-Propylalcohol 83.10 parts Pigment dispersion 5 Polyvinyl butyral (Esreck BBL-SH;  7.1 parts made by Sekisui Chemical Co., Ltd.) Pigment Yellow 180(C.I. No. 21290)  12.9 parts (Novoperm Yellow P-HG; made by ClariantJapan K.K.) Dispersing aid (Solsperse S-20000;  0.6 part made by ICI)n-Propyl alcohol  79.4 parts

[0430] Particle sizes of the thus obtained pigment dispersions 4 and 5were measured using a laser-scattering type particle sizedistribution-measuring meter, which indicated that the average particlesizes were 161 nm and 330 nm, respectively.

[0431] Next, the following ingredients were mixed under stirring toprepare a coating solution for a green image-forming layer.

[0432] [Formulation of a Coating Solution for the Green Image-FormingLayer] n-Propyl alcohol 321.5 parts Methyl ethyl ketone  89.3 parts Waxcompounds (Stearic amide “Newtron 2”; made by 0.824 part Nippon FineChemical Co., Ltd.) (Behenic amide “Diamid BM”; made by 0.824 partNippon Kasei Chemical Co., Ltd.) (Lauric amide “Diamid Y”; made by 0.824part Nippon Kasei Chemical Co., Ltd.) (Palmitic amide “Diamid KP”; madeby 0.824 part Nippon Kasei Chemical Co., Ltd.) (Oleic amide “DiamidO-200”; made by 0.824 part Nippon Kasei Chemical Co., Ltd.) (Erucicamide “Diamid L-200”; made by 0.824 part Nippon Kasei Chemical Co.,Ltd.) Rosin 2.360 parts (KE-311; made by Arakawa Kagaku Co., Ltd.)Polyvinyl butyral (Esreck B BL-SH; 1.455 parts made by Sekisui ChemicalCo., Ltd.) Pigment dispersion 4 77.11 parts Pigment dispersion 5 24.60Surfactant (Megafac F-176PF; solid 1.216 part content: 20%; made byDai-nippon Ink & Chemicals, Inc.)

[0433] Thermal transfer sheet Y, thermal transfer sheet M, thermaltransfer sheet C, thermal transfer sheet K, and an image-forming sheetare the same as in Example 1.

[0434] Thus, there was obtained a multi-color image-forming materialcomposed of the thermal transfer sheets G, Y, M and C, and theimage-receiving sheet.

EXAMPLE 4

[0435] Preparation of Thermal Transfer Sheet O (Orange)

[0436] A thermal transfer sheet O was prepared in the same manner aswith the preparation of the thermal transfer sheet R except for using acoating solution for an orange image-forming layer of the followingformulation in place of the coating solution for the red image-forminglayer. The thickness of the image-forming layer of the resulting thermaltransfer sheet O was 0.55 μm.

[0437] [Formulation of the Orange Pigment Dispersion Mother Liquor]Pigment dispersion 6 Pigment Orange 43 (C.I. No. 71105) 8.93 parts(Hosterperm Orange GR; made by Clariant Japan K.K.) Polyvinyl butyral(Esreck B BL-SH; 7.50 parts made by Sekisui Chemical Co., Ltd.)Dispersing aid (Solsperse S-20000; 0.47 part made by ICI) n-Propylalcohol 83.10 parts Pigment dispersion 7 Polyvinyl butyral (Esreck BBL-SH; 7.1 parts made by Sekisui Chemical Co., Ltd.) Pigment Yellow 180(C.I. No. 21290) 12.9 parts (Novoperm Yellow P-HG; made by ClariantJapan K.K.) Dispersing aid (Solsperse S-20000; 0.6 part made by ICI)n-Propyl alcohol 79.4 parts

[0438] Particle sizes of the thus obtained pigment dispersions 6 and 7were measured using a laser-scattering type particle sizedistribution-measuring meter, which indicated that the average particlesizes were 261 nm and 330 nm, respectively.

[0439] Next, the following ingredients were mixed under stirring toprepare a coating solution for an orange image-forming layer.

[0440] [Formulation of a Coating Solution for the Orange Image-FormingLayer] n-Propyl alcohol 321.5 parts Methyl ethyl ketone 89.3 parts Waxcompounds (Stearic amide “Newtron 2”; made by 0.824 part Nippon FineChemical Co., Ltd.) (Behenic amide “Diamid BM”; made by 0.824 partNippon Kasei Chemical Co., Ltd.) (Lauric amide “Diamid Y”; made by 0.824part Nippon Kasei Chemical Co., Ltd.) (Palmitic amide “Diamid KP”; madeby 0.824 part Nippon Kasei Chemical Co., Ltd.) (Oleic amide “DiamidO-200”; made by 0.824 part Nippon Kasei Chemical Co., Ltd.) (Erucicamide “Diamid L-200”; made by 0.824 part Nippon Kasei Chemical Co.,Ltd.) Rosin (KE-311; made by Arakawa Kagaku 2.360 parts Co., Ltd.)Polyvinyl butyral (Esreck B BL-SH; 1.455 parts made by Sekisui ChemicalCo., Ltd.) Pigment dispersion 6 84.10 parts Pigment dispersion 7 17.81Surfactant (Megafac F-176PF; solid 1.216 part content: 20%; made byDai-nippon Ink & Chemicals, Inc.)

[0441] Thermal transfer sheet Y, thermal transfer sheet M, thermaltransfer sheet C, thermal transfer sheet K, and an image-forming sheetare the same as in Example 1.

[0442] Thus, there was obtained a multi-color image-forming materialcomposed of the thermal transfer sheets 0, Y, M and C, and theimage-receiving sheet.

COMPARATIVE EXAMPLE 1

[0443] A multi-color image-forming material composed of theabove-mentioned thermal transfer sheet Y, M and C, and theimage-receiving sheet was prepared.

EXAMPLE 1a

[0444] Formation of a Transferred Image

[0445] The image-forming system was that shown in FIG. 4 using LuxelFINALPROOF 5600 as a recording apparatus. An image transferred toregular paper was obtained by the image-forming sequence of the systemand the method employed in the system for transferring to regular paper.

[0446] The image-receiving sheet (56 cm×79 cm) prepared above was woundand vacuum-absorbed onto a rotating drum of 38 cm in diameter providedwith vacuum section holes of 1 mm in diameter (surface density: 1 holefor an area of 3 cm×8 cm). Then, the thermal transfer sheet R, cut to 61cm×85 cm, was superimposed on the image-receiving sheet so as to stickout uniformly from the image-receiving sheet. While being squeezed bysqueeze rollers, the two sheets were joined and laminated by air-suctionthrough the section holes. The degree of reduced pressure with thesection holes thus covered was −150 mmHg (≈81.13 kPa) relative to 1atmosphere. The drum was rotated, and a semiconductor laser light with awavelength of 830 nm was focused to form a spot with a diameter of 7 μmon the surface of the light-to-heat conversion layer, and moved(subsidiary scanning) in a direction perpendicular to the rotationdirection (main scanning direction) of the recording drum, thusrecording a solid image on the laminate. The laser irradiationconditions were as follows. The laser beam used in this Example made useof a laser beam consisting of a multi-beam two-dimensional array formingparallelogram of 5 rows of beams in the main scanning direction and 3rows of beams in the subsidiary scanning direction. Laser power:  110 mWRotation number of the drum:  500 rpm Subsidiary scanning pitch: 6.35 μmEnvironmental tempera- 20° C., 40%; 23° C., 50%; 26° C., 65%. ture andhumidity: 3 condi- tions:

[0447] The diameter of the drum for exposure is preferably 360 mm ormore, and specifically a drum of 380 mm or more in diameter was used.

[0448] Additionally, the image size was 515 mm×728 mm, and theresolution was 2600 dpi.

[0449] After the laser image recording described above was completed,the laminate was removed from the drum, the thermal transfer sheet R waspeeled from the image-receiving sheet by hand, and the image on theimage-receiving sheet was further transferred to regular paper by meansof the following thermal transfer apparatus to obtain a solid image.

[0450] As the thermal transfer apparatus, a transfer apparatus was usedwhere in the material constituting the insertion support had a dynamicfriction coefficient to polyethylene terephthalate of 0.1 to 0.7, andthe conveying speed was 15 to 50 mm/sec. Also, the Vickers hardness ofthe material of the heat rolls in the thermal transfer apparatus ispreferably 10 to 100 and, specifically, heat rolls of 70 in the Vickershardness were used.

[0451] Also, in the same manner as above, each image was transferredonto the image-receiving sheet using the thermal transfer sheet Y, M orC in place of the above-mentioned thermal transfer sheet R, and, in thesame manner as above, a solid image of Y, M or C clor was obtained onregular paper.

[0452] Also, a laser light was imagewise iradiated successively on eachof the image-forming layers of the thermal transfer sheets R, C, M andY, and the irradiated portions were successively transferred andsuperimposed onto the image-receiving sheet to form a predeterminedmulti-color image on the image-receiving sheet, followed by transferringthe multi-color image to regular paper in the same manner as above.

COMPARATIVE EXAMPLE 1a

[0453] A solid image with a R color was obtained on regular paper bytransferring each image-forming layer on the image receiving sheet inthe same manner as in Example 1a except for successively using thethermal transfer sheets Y and M in place of the thermal transfer sheetR. Also, in the same manner as above, a solid image with a color of Y, Mor C was obtained on regular paper.

[0454] Also, a laser light was imagewise irradiated successively on eachof the image-forming layers of the thermal transfer sheets C, M and Y,and the irradiated portions were successively transferred andsuperimposed onto the image-receiving sheet to form a predeterminedmulti-color image on the image-receiving sheet, followed by transferringthe multi-color image on regular paper in the same manner as above.

EXAMPLE 2a

[0455] A solid image with a B color was obtained on regular paper bytransferring the image-forming layer on the image receiving sheet in thesame manner as in Example 1a except for using the thermal transfer sheetB in place of the thermal transfer sheet R. Also, in the same manner asabove, a solid image with a color of Y, M or C was obtained on regularpaper.

[0456] Also, a laser light was imagewise iradiated successively on eachof the image-forming layers of the thermal transfer sheets B, C, M andY, and the irradiated portions were successively transfered andsuperimposed onto the image-receiving sheet to form a predeterminedmulti-color image on the image-receiving sheet, followed by transferringthe multi-color image on regular paper in the same manner as above.

COMPARATIVE EXAMPLE 2a

[0457] A solid image with a B color was obtained on regular paper bytransferring each image-forming layer on the image receiving sheet inthe same manner as in Example 2a except for successively using thethermal transfer sheets M and C in place of the thermal transfer sheetB. Also, in the same manner as above, a solid image with a color of Y, Mor C was obtained on regular paper.

[0458] Also, a laser light was imagewise irradiated successively on eachof the image-forming layers of the thermal transfer sheets C, M and Y,and the irradiated portions were successively transferred andsuperimposed onto the image-receiving sheet to forma predeterminedmulti-color image on the image-receiving sheet, followed by transferringthe multi-color image on regular paper in the same manner as above.

EXAMPLE 3a

[0459] A solid image with a G color was obtained on regular paper bytransferring the image-forming layer on the image receiving sheet in thesame manner as in Example 1a except for using the thermal transfer sheetG in place of the thermal transfer sheet R. Also, in the same manner asabove, a solid image with a color of Y, M or C was obtained on regularpaper.

[0460] Also, a laser light was imagewise irradiated successively on eachof the image-forming layers of the thermal transfer sheets G, C, M andY, and the irradiated portions were successively transferred andsuperimposed onto the image-receiving sheet to form a predeterminedmulti-color image on the image-receiving sheet, followed by transferringthe multi-color image on regular paper in the same manner as above.

COMPARATIVE EXAMPLE 3a

[0461] A solid image with a G color was obtained on regular paper bytransferring each image-forming layer on the image receiving sheet inthe same manner as in Example 3a except for successively using thethermal transfer sheets C and Y in place of the thermal transfer sheetR. Also, in the same manner as above, a solid image with a color of Y, Mor C was obtained on regular paper.

[0462] Also, a laser light was imagewise irradiated successively on eachof the image-forming layers of the thermal transfer sheets C, M and Y,and the irradiated portions were successively transferred andsuperimposed onto the image-receiving sheet to form a predeterminedmulti-color image on the image-receiving sheet, followed by transferringthe multi-color image on regular paper in the same manner as above.

EXAMPLE 4a

[0463] A solid image with an O color was obtained on regular paper bytransferring the image-forming layer on the image receiving sheet in thesame manner as in Example 1a except for using the thermal transfer sheetO in place of the thermal transfer sheet R. Also, in the same manner asabove, a solid image with a color of Y, M or C was obtained on regularpaper.

[0464] Also, a laser light was imagewise irradiated successively on eachof the image-forming layers of the thermal transfer sheets O, C, M andY, and the irradiated portions were successively transferred andsuperimposed onto the image-receiving sheet to form a predeterminedmulti-color image on the image-receiving sheet, followed by transferringthe multi-color image on regular paper in the same manner as above.

[0465] The solid images and the multi-color images thus obtained wereevaluated as follows.

[0466] With the solid images transferred to regular papers, the maximumOD_(I) of the optical density was measured using a densitometer, X-rite938 (made by X-rite Co.) through a filter (shown in Table 1) which givesthe maximum optical density.

[0467] Also, hues of the solid images were measured by means of theabove-described densitometer X-rite 938, and elements L*, a* and b* inthe L*a*b* calorimetric system were determined. Additionally, theresults are shown in FIG. 1 on the a*b* plane.

[0468] Also, impressiveness of the letters and the background of themulti-color images formed were compared. O: impressive; X: unimpressive.

[0469] The results thus obtained are shown in Table 1. TABLE 1 Thicknessof Thermal OD_(I) Image-forming Impressiveness transfer Maximum Layer(μm) Hue of Letter or sheet Hue Value Filter (Ti) OD_(I)/T_(I) L* a* b*Background Example 1a R R 1.55 G 0.71 2.18 53.07 71.83 40.98 O Comp. Ex.1a Y + M R — — — — 45.84 68.57 51.99 X Example 2a B B 2.35 R 0.95 2.4719.79 25.70 −68.82 O Comp. Ex. 2a M + C B — — — — 21.57 30.55 −39.92 XExample 3a G G 1.34 R 0.70 1.91 61.80 −76.91 31.40 O Comp. Ex. 3a C + YG — — — — 52.40 −58.44 35.26 X Example 4a O O 1.51 B 0.55 2.75 68.6052.06 87.78 O Examples 1a to 4a, C C 1.59 R 0.45 3.53 58.59 −35.68−41.83 Comp. Ex. 1a to 3a, M M 1.51 G 0.38 3.97 46.69 74.78 −0.02 Y Y1.01 B 0.42 2.40 90.30 −5.55 96.55

[0470] Examples of the invention express hues in the color reproductionarea in the process color (Comparative Examples) and hues outside thearea. Hence, when used for letters or backgrounds, there can be formed amulti-color image with vivid colors and appealing power. Additionally,in FIG. 1, hues X reproducible by the Examples of the invention areoutside the hue area of conventional process colors (pentagonal hueregion shown by ○).

INDUSTRIAL APPLICABILITY

[0471] The multi-color image-forming material of the invention and themethod for forming a multi-color image can realize hues outside thecolor reproduction area in the process color, and therefore can realizehues that cannot have so far been provided, thus having the advantagethat the scope of reproducible hues being enlarged and the width ofdesigning being expanded.

1. A multi-color image-forming material for recording an image by: usingan image-receiving sheet having an image-receiving layer and at least 4kinds of heat transfer sheets, each of which is different from eachother in color and comprises a support having provided thereon at leasta light-to-heat conversion layer and an image-forming layer; superposingthe image-forming layer in each of the thermal transfer sheet on theimage-receiving layer of the image-receiving sheet, in which theimage-forming layer is opposed to the image-receiving layer; andirradiating a laser light thereto to transfer the laser-irradiated areaof the image-forming layer to the image-receiving layer of theimage-receiving sheet, wherein the multi-color image-forming materialincludes a heat transfer sheet (X) having an image-forming layercontaining one selected from Pigment Red 48:1, Pigment Red 48:3, PigmentGreen 7, Pigment Blue 15:6, Pigment Blue 60, Pigment Violet 23 andPigment Orange
 43. 2. The multi-color image-forming material asdescribed in claim 1, wherein the thermal transfer sheet (X) is athermal transfer sheet other than the thermal transfer sheet for a colorof yellow, magenta, cyan or black, and the hue of the image-forminglayer is outside the scope of hues reproducible by the single use orcombined use of the thermal transfer sheet for a color of yellow,magenta, cyan or black.
 3. The multi-color image-forming material asdescribed in claim 2, wherein the image-forming layer of the thermaltransfer sheet (X) has a hue of L*=48 to 58, a*=69 to 79, b*=36 to 46;L*=16 to 26, a*=19 to 29, b*=−63 to −73; L*=57 to 67, a*=−73 to −83,b*=26 to 36; or L*=65 to 75, a*=50 to 60, b*=81 to
 91. 4. Themulti-color image-forming material as described in any one of claims 1to 3, wherein the transferred image has a resolution of 2400 dpi ormore.
 5. The multi-color image-forming material as described in claim 4,wherein the transferred image has a resolution of 2600 dpi or more. 6.The multi-color image-forming material as described in any one of claims1 to 5, wherein the ratio of the optical density of the light-to-heatconversion layer of each of the thermal transfer sheets (OD_(LH)) to thethickness of the light-to-heat conversion layer (T_(LH)): OD_(LH)/T_(LH)(unit: μm) is 4.36 or more.
 7. The multi-color image-forming material asdescribed in any one of claims 1 to 6, wherein, the ratio of the opticaldensity (OD_(I)) to the thickness of the image-forming layer (T_(I)):OD_(I)/T_(I) (unit: μm) is 1.80 or more, in which OD_(I) represents themaximum optical density among the red filter, blue filter and greenfilter of the image-forming layer of each of the heat transfer sheet. 8.The multi-color image-forming material as described in any one of claims1 to 7, wherein the recording area of the multi-color image is of a sizeof 515 mm or more×728 mm or more.
 9. The multi-color image-formingmaterial as described in claim 8, wherein the recording area of themulti-color image is of a size of 594 mm or more×841 mm or more.
 10. Themulti-color image-forming material as described in any one of claims 1to 9, wherein the contact angle of the image-forming layer of each ofthe thermal transfer sheet with water and the contact angle of theimage-receiving layer of the image-receiving sheet with water are in therange of from 7.0 to 120.0°.
 11. The multi-color image-forming materialas described in any one of claims 1 to 10, wherein the contact angle ofthe image-receiving sheet with water is 86° or less.
 12. A method forforming a multi-color image, which comprises: using an image-receivingsheet having an image-receiving layer and at least 5 kinds of heattransfer sheets including thermal transfer sheets for a color of yellow,magenta, cyan or black, each of which comprises a support havingprovided thereon at least a light-to-heat conversion layer and animage-forming layer; superposing the image-forming layer of each of thethermal transfer sheet on the image-receiving layer of theimage-receiving sheet, in which the image-forming layer is opposed tothe image-receiving layer; and irradiating a laser light thereto totransfer the laser-irradiated area of the image-forming layer to theimage-receiving layer of the image-receiving sheet and record an image.13. The method for forming a multi-color image as described in claim 12,which at least uses the multi-color image-forming material described inany one of claims 1 to 11.